Abstract: Apparatus for detecting light scattered by a small particle (e.g., a blood cell) irradiated by a light beam comprises one or more photodetectors and a plurality of optical fibers that serve to optically couple the scattered light and the photodetector(s). To enhance the efficiency of such optical coupling, a portion of each of the optical fibers in the vicinity of its light-collecting end is supported so that its optical axis extends towards the light-scattering source. By this arrangement, scattered light enters each fiber from a direction substantially parallel to the fiber axis. Preferably, the light-collecting ends of the optical fibers are supported on a concave surface and so that the respective optical axes of the fibers converge at a point representing the apparent position of the light-scattering source, taking into account the refractive effects of an optical flow cell through which scattering is detected.

Abstract: A particle size distribution analysis apparatus comprising a sample measurement zone adapted to define a sample of particles, a light emitting means adapted to provide a source of light incident upon the sample measurement zone, and at least a first detection means adapted to measure light levels in the apparatus at particular scattering angles and output a signal to a computation means enabling the particle size distribution of particles contained within the sample to be determined, wherein the computation means is adapted, in use, to calculate a particle size distribution taking into account reflections by the measurement zone of light scattered off the particles.

Abstract: A method of processing a semiconductor device is provided with several steps, including the step of generating plasma in a processing chamber to form or process a thin firm on a semiconductor device. The step of scanning, through a window, intensity modulated laser beam, which is modulated at a desired frequency inside the processing chamber where the semiconductor device is being processed. The step of receiving by a sensor through the window a back scattered light being scattered from fine particles suspended in the processing chamber by the scanning laser and detecting the desired frequency component from a signal outputted from the sensor. From the detected frequency component information relating to quantity, size, and distribution of the fine particles illuminated by the laser beam inside the processing chamber is obtained. This information is then outputted.

Abstract: Characterizing a powder bed includes generating measurements by repeating the following. A location of the powder bed is illuminated with light having a time varying intensity with a resolution of less than one hundred nanoseconds. The particles scatter the light to alter the time varying intensity. The light propagates through a portion of the particles that defines a sampled volume. The light received from the powder bed is detected. The altered time-varying intensity of the light is measured to generate a time-dependent signal having a time-dependence that is less than or equal to a time-of-flight of a photon of the propagating light. An optical property is determined from the time-dependent signal, and a characteristic is determined from the optical property. The sampled volume is determined, and variance of the measurements is calculated. Uniformity of the powder bed is determined in accordance with the variance and the sampled volume.

Abstract: A distance sensor having a sensor for a motor vehicle in which an arrangement is provided by which gnment angles and trajectory curvatures can be compensated for during travel not only on a straight road but also along curves. In a sensor mounted displaced from the center line of the vehicle, an angle (alpha_sensor) is measured which cuts the projected center line of the motor vehicle at the target object, a vehicle driving ahead. By the additional use of a yaw rate sensor, curve curvatures of the road are also compensated for, so that angle and distance measurement can also be made along curves.

Abstract: A method and apparatus for reducing speckle due to MSL, without any loss of resolution, by averaging over different angles of the incident light at low input resolution, while collecting the backscattered light at a full resolution of a lens is described. The present invention allows discrimination against the speckle due to coherent MSL.

Abstract: A micropulse lidar system is described that comprises, a laser light source for emitting a pulsed laser beam, beam shaping means for shaping the intensity distribution of said beam such that said beam has a substantially annular intensity distribution in cross-section, a Schmidt-Cassegrain telescope for transmitting the annular beam to an atmospheric target and for collecting backscattered light returned from said target, and means for detecting and analyzing said backscattered light. The system has higher efficiency and better signal-to-noise ratio than a corresponding system without the beam shaping means. There is also disclosed a method for optimising the design of the beam shaping means.

Abstract: A method for controlling both the scattering and absorption of electromagnetic waves. The method is based on prescribing the sizes of the particles that are suspended in a specified medium and a ratio of the refractive indices of the particles and the medium. This method can be used in applications that require maximizing or minimizing scattering of electromagnetic waves. The present method can also be used in applications that require maximizing or minimizing absorption of electromagnetic waves. Further, the invention provides control of backscattering (radar cross section) and, controlling any combination of scattering, absorption and backscattering of electromagnetic waves. Applications for the present method include stealth technology, friend or foe identification, and defensive screening.

Abstract: A back-scatter detector for detecting light scattered backwardly (i.e., reflected) by an irradiated particle such as a blood cell comprises a plurality of optical fibers. A fiber optic holder having a centrally located opening for passing a light beam used to irradiate particles at a particle-interrogation zone serves to position the light-collecting ends at a desired position to collect back-scattered light. Preferably, the light-collecting ends of the optical fibers are positioned in a circular pattern centered about the irradiating light beam, and the respective axes of the supported portions of the optical fibers extend either parallel to the beam axis, or, more preferably, so that they converge at or near the location of the scattering source, i.e., the irradiated particle or cell. The latter configuration assures that the back-scatter light enters the fiber end substantially parallel to the fiber axis, thereby reducing optical transmission loses in the fiber.

Abstract: Blood cells of interest are readily distinguishable from other blood cells and look-a-like particles found in a blood sample by their back-scatter signature. A preferred method for differentiating platelets in a blood sample is to irradiate the cells and particles, one at a time, with a beam of radiation, and to detect back-scattered (reflected) radiation using a plurality of optical fibers to transmit the back-scattered radiation to a high-gain photodetector, e.g. a photomultiplier tube. Preferably, the back-scatter signal so obtained is combined with a second signal representing, for example, either the level of forward-scatter within a prescribed, relatively narrow angular range, or the level of side-scattered radiation, or the level of attenuation of the cell-irradiating beam caused by the presence of the irradiated cell or particle in the beam, or the electrical impedance of the irradiated cell or particle, to differentiate the cells of interest.

Abstract: Apparatus for detecting light scattered by a small particle (e.g., a blood cell) irradiated by a light beam comprises one or more photodetectors and a plurality of optical fibers that serve to optically couple the scattered light and the photodetector(s). To enhance the efficiency of such optical coupling, a portion of each of the optical fibers in the vicinity of its light-collecting end is supported so that its optical axis extends towards the light-scattering source. By this arrangement, scattered light enters each fiber from a direction substantially parallel to the fiber axis. Preferably, the light-collecting ends of the optical fibers are supported on a concave surface and so that the respective optical axes of the fibers converge at a point representing the apparent position of the light-scattering source, taking into account the refractive effects of an optical flow cell through which scattering is detected.

Abstract: Preferred embodiments of the present invention utilize a plurality of spectroscopic techniques to measure characteristics of tissue useful in the diagnosis of disease. Fluorescence, reflectance and light scattered spectra can be measured and processed to determine the size, distribution and/or composition of tissue. The methods and systems can be used particularly in the early detection of carcinoma within tissue in vivo and in vitro.

Abstract: A process and an apparatus preferably used during the photocagulation of the fundus of human eyes or animals measures density fluctuations caused by pulsed irradiation, such as a laser irradiation source, on a material. A wherein a measuring signal is acoustically or optically detected. The change of the intensity and/or of the time slope of the measuring signal resulting from the irradiation of a specific material point is detected. A linear thermo-elastic signal fraction is removed from the measuring signal.

Abstract: A method and system for minimizing inter-coefficient crosstalk in imaging the internal properties of a scattering medium. The method and system minimizing inter-coefficient. crosstalk in image reconstruction by solving a system of linear perturbation equations with the use of relative detector values, weight matrix scaling, and constraints based on either the know or unknown direction of the perturbations in the medium's properties. The constraint being either (1) positive or negative corresponding to the direction of a known perturbations, or (2) solving the system of equations with both positive and negative constraints and summing the results where the direction of the perturbations are unknown. The advantages of the inventive method and system result in effective isolation of absorption and scattering coefficient variations, even for complex combinations of perturbations in these coefficients.

Abstract: The present invention relates to an optical system for an apparatus for multi-part differential particle discrimination to facilitate analysis, classification, and sorting of various fluid components for presentation. The optical system is characterized by one or more of the following: a synchronized illumination beam and flow cell conduit, a flow cell arrangement to control back reflection, and light sensor arrangement to particularly gather a specific range of light scatter, such specific range of light scatter directly corresponding to at least one type of particle capable of being identified by the apparatus.

Abstract: An apparatus and a method are disclosed for separating light remitted by a target into a directly scattered light component and at least one multiply scattered light component, detecting the components at least substantially simultaneously, and forming independent sets of image information from each component. The apparatus and the method can be employed in conjunction with techniques such as scanning and tomography to attain precise imaging of biological tissue, including the retina of the eye.

Abstract: A radiation sensing method and device that is used to measure physical properties of materials over a wide dynamic range. The sensor (20) comprises multiple radiation sources and multiple detectors at multiple separation distances. The detected signals from the different sources are separated and then combined mathematically in a manner such that the combination is self-compensated for both component drift and changes in radiation coupling efficiency between the source or detector and the material of interest. In a preferred embodiment, the biomass in a liquid cell culture (54) is measured with high accuracy over a wide dynamic range using optical wavelength radiation. The measurement can be made with the sensor external to the liquid culture container in a manner that is compensated for the thickness of the container window (50).

Abstract: The present invention provides a particle-measuring system and the particle measuring method that is provided in a processing system for generating an atmosphere including atmospheric air or a gas exhausted from within a processing chamber by a vacuum pump, and for processing a wafer W relating to a semiconductor manufacturing in this atmosphere, and that is installed on an exhaust pipe connecting between an exhaust opening of the processing chamber and the vacuum pump, for measuring the number of particles included in the exhaust gas.

Abstract: A fluid quality sensor system comprising a light source, a first light sensitive element disposed at a distance from the light source, forming a gap having dimensions suitable for permitting a fluid to flow therebetween, and aligned with the light source to receive light transmitted by the light source through the fluid, a second light sensitive element disposed perpendicular to a midpoint of a light path between the light source and the first light sensitive element, and a third light sensitive element disposed so as to form an acute angle at the midpoint with the light source.

Abstract: The present invention relates to systems and methods for examining a sample using a substantially monostatic, substantially confocal optical system comprising transmitting optics that focus an illuminating light upon the sample and receiving optics that collect light emitted from the sample following illumination thereof. In certain embodiments, the receiving optics may be arranged circumferentially around the light path traversed by the illuminating light. In certain embodiments, video apparatus may be included to produce images or to align the system in proximity to the target tissue. The systems and methods of the present invention may be directed towards the examination of a body tissue to provide a medical diagnosis.

Abstract: A fume sensor system that measures the concentration of fume particulate in a boiler and suppresses background noise.

Abstract: A method and a system is provided for discriminating between healthy cervical tissue and pathologic cervical tissue based on the fluorescence response of the tissue to laser excitation (LIF) and the backscatter response to illumination by white light (in the spectral range of 360 to 750 nm). Combining LIF and white light responses, as well as evaluating a spatial correlation between proximate cervical tissue sites in conjunction with a statistically significant “distance” algorithm, such as the Mahalanobis distance between data sets, can improve the discrimination between normal and abnormal tissue. The results may be displayed in the form of a map of the cervix representing the suspected pathology.

Abstract: An optical monitoring unit includes a transmitting unit having plural light emitting diodes that are connected together two at a time in respective diode pairs. Each diode of each diode pair is respectively selectively connectable to a current source so as to operate as an active transmitting diode, or to a load resistor across which a voltage may be measured so as to operate as a monitoring diode. When any selected single diode is operated as the transmitting diode, its light output is measured and evaluated by operating the other diode of the pair as the monitoring diode, which receives optical crosstalk from the light output of the transmitting diode and correspondingly generates a photoelectric current through the load resistor.

Abstract: An automatic setup backscatter particulate monitor includes a small source (38) of narrow beam radiant energy directed into a gas stream containing particulates. A lens (34) that is mounted behind the radiant energy source (38) collects the energy reflected back from the particulates and concentrates it on a photodetector (48). The beam is directed into duct at an angle greater than twice the beam spread, minimizing reflection off opposing wall surfaces. Internal radiant energy sources are periodically directed to the detector to verify system integrity. Backscattered energy is corrected for energy reflected from the opposite stack wall and for ambient energy.

Abstract: An optical probe for analyzing a sample illuminated by a laser includes an input optical fiber operably connectable to the laser where the input optical fiber has an entrance end and an exit end. The probe also includes a first beam splitter where the first beam splitter is adapted to transmit an alignment portion of a light beam from the input fiber exit end and to reflect a homodyning portion of the light beam from the input fiber. The probe also includes a lens between the input fiber exit end and the first beam splitter and a first and a second output optical fiber, each having an entrance end and an exit end, each exit end being operably connectable to respective optical detectors. The probe also includes a second beam splitter which is adapted to reflect at least a portion of the reflected homodyning portion into the output fiber entrance ends and to transmit light from the laser scattered by the sample into the entrance ends.

Abstract: The present invention relates to a backscattering apparatus and method for optical scanning along a circular path using one or more optical illuminators and receivers. More particularly, it relates to an apparatus and method of focusing one or more beams of light into one or more beam spots, scanning the common beam spot(s) across a circular path and receiving light backscattered from the beam spot(s) with one or more detectors. A rotationally mounted scanning optics having an optical axis parallel to but not coaxial with the axis of rotation is used to accomplish these functions. A motor may be operatively linked to the scanning optics to cause the same to rotate at a constant angular velocity whereby, with appropriate signal generating detector and signal processing electronics, the number and size of particles suspended in a fluid medium exposed to the beam spot(s) can be determined.

Abstract: A radar system which is used for determining optical range includes a frequency analyzer for the analysis of differential frequency signals, which originate from a mixture of the transmitted signal with the received signals, for example reflected from a fog bank. The frequency spectrum images the distance profile of the fog bank.

Abstract: A method and a system is provided for discriminating between healthy cervical tissue and pathologic cervical tissue based on the fluorescence response of the tissue to laser excitation (LIF) and the backscatter response to illumination by white light (in the spectral range of 360 to 750 nm). Combining LIF and white light responses, as well as evaluating a spatial correlation between proximate cervical tissue sites in conjunction with a statistically significant “distance” algorithm, such as the Mahalanobis distance between data sets, can improve the discrimination between normal and abnormal tissue. The results may be displayed in the form of a map of the cervix representing the suspected pathology.

Abstract: Reducing blind spots of a laser radar observing wake turbulence is required for detecting efficiently the wake turbulence which appears behind the main wings of an aircraft and affects the flight of other aircraft. A first laser radar a and second laser radar each emit a laser beam from different positions. A signal processing device produces wake turbulence information based on the reception signal of the first and second laser radar. Further, the signal processing device specifies wake turbulence information for producing display data either by making a composite of wake turbulence information of two laser radar whose observation areas do not overlap each other or by selecting the larger value of wake turbulence information from two laser radars whose observation areas overlap each other and produces display data for indicating wake turbulence information on monitor display based on the specified wake turbulence information.

Abstract: The invention relates to a method and a device for in vivo detection of the direction of Langer's lines in the skin. Light is irradiated into the skin as primary light at one defined site (7) identified through the epidermis (6) in such a way that it is transported in the skin (5) by scattering or absorption, while part of said irradiated light emerges from the skin as secondary light in the region surrounding the irradiated site. An amplitude-dependent property of secondary light emerging from the skin (5) around the irradiated site is measured in order to determine the preferential direction of the diffuse light transport in the skin (5) and, consequently, determine the orientation of Langer's lines thereof.

Abstract: The apparatus is designed to examine a surface 9 and comprises a polarization analyzer element 14, or analyzer, placed in the path of a light beam 17 reflected by the said surface 9, a means for taking digital images 13 placed in the path of the beam 17 reflected by the said surface 9 downstream of the analyzer 14, and a processing unit 15 capable of calculating the brightness and the intensity of a plurality of pixels of at least one image.

Abstract: Light is made incident into an inhomogeneous medium, and transmitted light or reflected light is detected. The intensity of the detected light is represented by the linear sum of exponential functions of penetration depth using e as a base, or a function formed from the exponents and a function derived from the function. This function includes the physical quantity of the inhomogeneous medium as a coefficient. When light amount measurement data are acquired at a plurality of wavelengths or thicknesses, and the light intensity or other known information is substituted into the function and an expression derived from the function, the physical quantity of the inhomogeneous medium can be determined. Thus, an optical analysis method for an inhomogeneous medium, which is capable of accurate analysis, can be provided.

Abstract: An integrating nephelometer is modified to measure 180° backscattering from an aerosol. A laser is mounted outside a housing of the nephelometer and produces a coherent light beam that is directed into a sample volume of the nephelometer, substantially along an optical sensing axis (<4° off the optical axis). Light from the laser beam that is reflected by an aerosol travels back along the optical sensing axis toward a photomultiplier tube (PMT) light detector, which thus produces a signal indicative of the backscattering from the aerosol. A portion of the laser beam is conveyed into the housing of the nephelometer through an optical fiber for use as a reference beam. A motor-driven chopper disk disposed across the optical axis is divided into an open sector, a calibration sector (with a very low transmission), and a flat black light absorbing sector.

Abstract: A laser is used to radiate a non-homogeneous body comprising two or more materials, with varying scattering characteristics with reference to the radiation. The ballistic or snake radiation is detected as reflected radiation form incident points in the radiation light path and use to construct data indicative of one or more features of the body such as the interface between two of the varying characteristic materials which are in the radiation light path.

Abstract: An optical measurement system for determining transmitted radiation and scattered radiation in a liquid sample contained in a capillary tube and subject to measurement radiation, is provided with a first detector picking up transmitted radiation, which is positioned close to or on the axis of the beam of measurement radiation. There is further provided a second detector for picking up scattered radiation, which is positioned at a distance from the first detector in the direction of the capillary axis. The two detectors lie on different sides of a plane which contains the capillary axis and is normal to the axis of the measurement radiation.

Abstract: Two-photon absorption measurements are made at various points remote from monitoring apparatus by apparatus which includes two lasers that produce counter-propagating beams through the earth's atmosphere. The lasers are tuned such that the sum of the energies of the photons in each of the laser beams equals that associated with a predetermined transition of a gas in the earth's atmosphere. In one embodiment, a pulsed laser and a CW laser are used. The pulse from the pulsed laser propagates along the CW beam produced by the CW laser and overlaps the CW beam at positions determined by a range gating technique, which makes possible the measurement of the two photon absorption at the various positions of overlap or coincidence. In one embodiment, the subject apparatus is utilized for pollution monitoring, in which the frequencies of the lasers are tuned such that the energies of the photons from these lasers add up to a transition of a predetermined pollutant.

Abstract: An ocular blood-flow meter includes an optical system for applying measuring light to a blood vessel of a subject eye, and for receiving light scattered by the blood vessel of the subject eye. A mechanism is provided for changing a direction in which the measuring light is applied and a direction in which the scattered light is received so as to enable a plurality of measurements in different directions. A controller performs the plurality of measurements in the different directions by using the optical system and the mechanism so as to obtain information concerning a blood flow. An output device provides a received-light signal obtained by the optical system or the information concerning the blood flow. An input device enables an operator to select a re-measurement operation in a desired direction from the different directions and to instruct the selected re-measurement operation.

Abstract: A method for measuring the end point and for monitoring the real time kinetics of a bioaffinity reaction in biological fluids and suspensions, employing microparticles as bioaffinity binding solid phase, biospecific reagent labelled with a fluorescent label and a fluorescence detection system which is based on two-photon fluorescence excitation, contacting the analyte, the labelled reagent and the solid phase simultaneously, focusing a two-photon exciting laser beam into the reaction suspension and measuring the fluorescence signal emitted by the microparticles from one particle at a time when they randomly float through the focal volume of the laser beam. In this method the signal is monitored kinetically to obtain information about the analyte concentration before the reaction approaches the highest point of the response. Since the growth rate of the signal intensity is directly proportional to the analyte concentration, the analyte concentration can be predicted in the initial phase of the reaction.

Abstract: The present invention relates to a mass-flow sensor that measures the mass flow of conveyed reflective materials, such as cotton, in a stream of air or non-opaque fluid. In particular, the mass-flow sensor of the present invention may be used with a GPS receiver as a cotton yield monitor when mounted on a cotton harvester. It can also be used to measure mass flow of the various cotton component streams in a cotton gin. The mass flow measurements may be made non-intrusively and in real time. The present invention also relates to a method for measuring mass flow using the mass-flow sensor of the present invention.

Abstract: A homogeneous biospecific assay method for an analyte in solution or in a biological suspension, in which a biospecific reagent competitively binding an analyte and a ligand labeled with a fluorescent molecule, is reacted with and bound to a solid phase, and in which the free labeled ligand is extracted is excited with two-photon excitation by focusing a laser beam suitable for two-photon excitation into the sample volume; and the concentration of the analyte is calculated based on the photon emission contributed by the free labeled ligand.

Abstract: The present invention provides a method and an apparatus for the in vivo, non-invasive, early detection of alterations and mapping of the grade of these alterations, caused in the biochemical and/or in the functional characteristics of epithelial tissues during the development of tissue atypias, dysplasias, neoplasias and cancers. The method is based, at least in part, on the simultaneous measurement of the spatial, temporal and spectral alterations in the characteristics of the light that is re-emitted from the tissue under examination, as a result of a combined tissue excitation with light and special chemical agents. The topical or systematic administration of these agents result in an evanescent contrast enhancement between normal and abnormal areas of tissue. The apparatus enables the capturing of temporally successive imaging in one or more spectral bands simultaneously.

Abstract: The invention relates to a method for determining the spatial concentration of the various components of a mixture, in particular of a gas mixture in a combustion chamber, of a motor for example; a laser beam is hereby directed into the combustion chamber; the laser beam brings the particles of the mixture to radiate, whereas this light of the particles is passed backward through a masked lens and is imaged on a display as a radiating surface and the radial intensity distribution is recorded by an array photodetector, whereas the spatial concentration of individual components of the particle mixture may be measured from the radial intensity distribution.

Abstract: A scanning module for imaging through scattering media is provided. The scanning module image through scattering media while alleviating adverse effects of the weak transmission through highly scattering media. The injection of photons is optimized so that the overall transmission is increased compared to the conventional art. Cross-talk effects in a multi-port geometry are eliminated thereby increasing parallelism.

Abstract: A smoke detector includes a housing defining a dark chamber admitting test atmosphere. A light receiver is disposed within the chamber. A scatter emitter is positioned within the chamber such that light strikes the receiver when reflected off particles suspended in the test atmosphere. An obscuration emitter is positioned within the chamber such that light emitted is directed to the receiver unless obstructed by particles suspended in the test atmosphere. A smoke detect signal is generated responsive to a measurement made responsive to the scatter emitter and/or the obscuration emitter.

Abstract: An optical detection system and method is disclosed comprising a first light guide for conveying light energy from a light source to a first light guide face end that is immersed in a dispersant medium. A first portion of the light energy exits the face end to irradiate particles contained in the dispersant medium and a second portion of the light energy is reflected by the face end back into the first light guide. A frequency transducer mounted to the first light guide receives at least one specific frequency from a range of frequencies generated by a frequency oscillator and oscillates the first light guide face end at the applied specific frequency. The transducer oscillations are further coupled into the dispersant medium, causing the dispersant medium and the particles contained therein to oscillate at the oscillation frequency of the first light guide face end.

Abstract: A high altitude lidar system propagates a beam of laser pulses through clearings in a cloud formation which reflects off the surface of the earth thereby providing first earth surface returns and reflections towards the base of a cloud that again reflects the pulses back towards the earth surface to be reflected again to provide cloud base returns. The time differential between the earth surface returns and the cloud base returns are used to determine the altitude of the base of the cloud.

Abstract: Light rays of a plurality of wavelengths which are modulated in intensity with a plurality of different frequencies are irradiated on a plurality of irradiation positions on the surface of a living body, and time-variable changes in living body transmitting light intensity levels corresponding to the respective wavelengths and the respective irradiation positions are measured at different positions on the surface of the living body. After completion of the measurement or during the measurement, changes in concentration values of absorbers in the living body are determined from the living body transmitting light intensity levels of the plurality of wavelengths detected at the respective detection points and a measuring point is set on a perpendicular extending through an intermediate point between the incident point and each detection point so as to image a function of the living body.

Abstract: An apparatus for separating an image of a target into a directly scattered component and a multiply scattered component by providing a stationary field stop having a first region and associated detector confocal to a point on the target. During a first interval, a light source directs a first beam to the target and the directly scattered component is selected by the first region. During a second interval, the light source directs a second beam to the target and the multiply scattered component us selected by the first region and its associated detector. Alternatively, a light source directs a first beam to the target and the directly scattered component is selected by the first region of the field stop and its associated detector, while the second region and its associated detector select for multiply scattered light.

Abstract: A smoke detector includes a housing defining a dark chamber admitting test atmosphere. A light receiver is disposed within the chamber. A scatter emitter is positioned within the chamber such that light strikes the receiver when reflected off particles suspended in the test atmosphere. An obscuration emitter is positioned within the chamber such that light emitted is directed to the receiver unless obstructed by particles suspended in the test atmosphere. A smoke detect signal is generated responsive to a measurement made responsive to the scatter emitter and/or the obscuration emitter.

Abstract: A particle size distribution analysis apparatus wherein there are provided a sample measurement zone adapted to contain a sample of particles, a light emitting means adapted to provide a source of light incident upon the measurement zone, and a detection means adapted to measure light levels at different scattering angles and to output signals to a computation means, enabling the size of particles contained within the sample to be determined, wherein the light emitting means comprises a first light source emitting a substantially monochromatic first wavelength of light and a second light source emitting a substantially monochromatic second, different, wavelength of light.