Abstract: A method for determining the number or concentration of virus particles in a sample by use of a light scattering detector. The method may be used to quantitate purified virus preparations or virus samples containing contaminants, including ultraviolet light-absorbing contaminants, such as proteins. The method is useful for quantitation of viruses for use in gene therapy, oncolytic viruses for tumor cell lysis and virus-based vaccines.

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: In detecting a boundary line between areas different in light reflectance, it has so far been impossible to specify the boundary line at a distance shorter than the arrangement pitch of photodetectors (pixels) arranged in the camera. In the present invention, luminance variations near the boundary line between areas different in light reflectance are derivated. Further, in unit blocks G corresponding to pixels and arranged in a direction (Y direction) in which the boundary line extends, derivated values of luminance for each row of unit blocks are added and then a variation curve of the added values of derivated luminance values in unit block rows is drawn to specify a peak position thereof and also specify the position of the boundary line X0. Thus, it is possible to specify the position of the boundary line with a high accuracy at a distance shorter than the unit block pitch.

Abstract: A method for determining the number or concentration of virus particles in a sample by use of a light scattering detector. The method may be used to quantitate purified virus preparations or virus samples containing contaminants, including ultraviolet light-absorbing contaminants, such as proteins. The method is useful for quantitation of viruses for use in gene therapy, oncolytic viruses for tumor cell lysis and virus-based vaccines.

Abstract: The present invention includes a method and an apparatus for the quantitative determination of particles in fluid. The apparatus of the invention includes an emitters set of one or more light emitters, in combination with a detector set of one or more light detectors sensitive to the output of the emitters. During analysis of the sample, data from a plurality of signal paths between the emitter and detector sets are gathered. This information is subsequently evaluated by comparison with known data for different fluid particle contents. Some differentiation between different particles in a fluid sample are possible in many embodiments. Typical uses include analysis of milk and dairy fluids, blood samples, lubricants, suspensions of pigments, etc.

Abstract: An automated nucleic acid compaction device for analyzing and compacting a nucleic acid complex into unimolecular nucleic acid particles. Broadly, the device includes a container support and agitation system; a measuring and testing system; and a dispensing system; all controlled by a control system. The control system controls the support and agitation system and the dispensing system based either on a predetermined formulation or by analysis of feedback data provided by the measuring and testing system. In a preferred embodiment, the device is a real-time measuring and mixing instrument operating in a closed loop system. The preferred embodiment also comprises a monitoring system including a submersible probe which is positioned in the batch solution to provide data to a controller. Once a desired level of nucleic acid compaction is reached, as detected by the monitoring system, the controller stops the dispensing and mixing agitating systems.

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: An apparatus for measuring particle size distribution comprises an electric mobility classifying section (11) that comprises an outside electrode (12), an inside electrode (13) and an annular cylindrical hollow portion (14) defined by the outside and inside electrodes, a particle size measuring section (21) that is disposed under the electric mobility classifying section for measuring particle size distribution, and a guide frame (31) that allows the electric mobility classifying section and the annular cylindrical hollow section to communicate with each other. A sample gas containing charged particles under measurement is supplied from above into the annular cylindrical hollow section of the electric mobility classifying section to classify the particles according to their electric mobilities. The gas containing the classified particles is supplied into the particle size measuring section via the guide frame to directly obtain approximate particle sizes.

Abstract: A method of transporting a reticle is disclosed. The reticle is placed in a reticle carrier that has an ionizer. Moreover, the reticle may be attached with a pellicle. The pellicle consists of a pellicle frame and a pellicle film stretched over the pellicle frame. The pellicle frame has included within an absorbent material.

Abstract: A particle size distribution measuring apparatus includes a source of laser light for providing a laser beam to a sample cell that can hold a sample to be measured. A condenser lens converges the laser beam towards the sample cell along an optical axis. The position on the other side of the sample cell is a ring detector unit that can be aligned with the optical axis to measure light intensity at relatively small scattering angles from contact with particles in the sample cell. An array of detectors can be operatively positioned on a substrate with appropriate amplifying multiplying and analog to digital conversion capacity for measuring light intensity at relatively large scatter angles. The outputs of the ring detector unit and the array of detectors can be used to determine the particle size distribution of particles in the sample.

Abstract: The present invention is directed to a system for converting between single flow and split flow evaporative light scattering detection devices for detecting samples in a mobile phase. Included in the system is a evaporative light scattering detection device, a low temperature adaptor, and a connection tube for providing a fluid connection between the evaporative light scattering detection device and the low temperature adaptor.

Abstract: A method and apparatus for differentiating and enumerating the five major sub-populations of leukocytes in a blood sample (i.e., lymphocytes, monocytes, eosinophils, neutrophils and basophils) uses multiangle light scatter and DC (Coulter) volume measurements. Light scattering characteristics of the leukocytes are determined within five different angular ranges, all being lower than 40 degrees. The invention is particularly useful in differentiating and enumerating the basophil sub-population which has heretofore required more complex apparatus and/or chemical processing.

Abstract: An automatic dilution system and method provides optimal dilution factor DF for a sample suspension containing particles mixed with a diluent. A diluent flows into a mixing chamber, and the sample is injected into the chamber. A sensor, such as a single particle optical sensor (SPOS), measures the value of a particular characteristic, which characteristic Rmax(0) is the initial rate of increase of a quantity related to particle concentration. A CPU/Controller calculates from Rmax(0) the optimal value of DF, and develops a control signal which adjusts the flow of the sample to provide the optimal value of DF. In a first embodiment, all of the diluted sample passes through the sensor. In a second embodiment, only a portion of the sample is directed through the sensor to shorten the time to reach equilibrium. The time to reach equilibrium is further reduced in a third embodiment in which the mixing means is a static mixer, having relatively small volume, inserted in series with a diluent flow tube.

Abstract: A system for simultaneously inspecting the frontsides and backsides of semiconductor wafers for defects is disclosed. The system rotates the semiconductor wafer while the frontside and backside surfaces are generally simultaneously optically scanned for defects. Rotation is induced by providing contact between the beveled edges of the semiconductor wafer and roller bearings rotationally driven by a motor. The wafer is supported in a tilted or semi-upright orientation such that support is provided by gravity. This tilted supporting orientation permits both the frontside and the backside of the wafer to be viewed simultaneously by a frontside inspection device and a backside inspection device.

Abstract: A system for controlling the deglycerolization of red blood cells includes a cell sorter having multiple fluid channels each having a unique cross-sectional area for directing a fluid mixture consisting essentially of a saline solution and a plasma solution having glycerized red blood cell products through one or more of the fluid channels based on the sizes of the red blood cell products. An optical energy source illuminates the fluid mixture in the cell sorter, whereupon an optical detector generates a data signal in response to receiving light signals that propagate through the fluid mixture. A processor generates a control signal in response to receiving the data signal that is used by a servo-controlled device to control the ratio of the saline and plasma solutions in the fluid mixture so that the red blood cell products substantially flow only through one or more of the fluid channels having particular cross-sectional areas.

Abstract: An apparatus and method for measuring a particle size distribution comprising a light source directing a laser light to particles which are dispersed into a solvent and which exhibit Brownian motion, a detector converting an interference light caused by Doppler-shifted scattered light by the particles into an electric detection signal, an operation unit obtaining an intermediate function by processing the detection signal, and a processing unit subjecting the intermediate function to an inverse problem and thereby calculating a particle size distribution. The apparatus includes a data selecting unit between the operation unit and the processing unit for selecting data from all data regions in the intermediate function at appropriate intervals and creating a data table used in an inverse problem.

Abstract: Multiple independent spectral measurements of light reflected from a target are produced concurrently by illuminating the target with a train of laser pulses wherein the train of pulses produces a line spectrum within the illuminating signal. A characteristic dimension of the receiving aperture is established based on illuminating wavelength, a cross-sectional dimension of illuminated region of a target, and the range between a target and the receiving aperture or image plane. The characteristic dimension corresponds to the spacing of peaks in a speckle pattern of an image plane. The use of multiple receiving telescopes having the characteristic dimension allows for independent measurements concurrently by each of the receiving telescopes. The train of illuminating pulses is generated by mode-locked operation of the laser for synchronization of sinusoidal components at line frequencies of the pulse train spectrum, and wherein the spacing of the spectral lines is at least a decorrelation frequency.

Abstract: A method and apparatus for interrogating a target having a plurality of plasmon resonant particles (PREs) distributed in the target are disclosed. In the method, a field containing the target is illuminated, and one or more spectral emission characteristics of the light-scattering particles in the field are detected. From this data, an image of positions and spectral characteristic values in the field is constructed, allowing PREs with a selected spectral signature to be discriminated from other light-scattering entities, to provide information about the field. Also disclosed are a novel PRE composition for use in practicing the method, and a variety of diagnostic applications of the method.

Abstract: A visible light method for detecting sub-100 nm size defects on mask blanks used for lithography. By using optical heterodyne techniques, detection of the scattered light can be significantly enhanced as compared to standard intensity detection methods. The invention is useful in the inspection of super-polished surfaces for isolated surface defects or particulate contamination and in the inspection of lithographic mask or reticle blanks for surface defects or bulk defects or for surface particulate contamination.

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.

Abstract: Rapid characterization and screening of polymer samples to determine average molecular weight, molecular weight distribution and other properties is disclosed. Rapid flow characterization systems and methods, including liquid chromatography and flow-injection analysis systems and methods are preferably employed. High throughput, automated sampling systems and methods, high-temperature characterization systems and methods, and rapid, indirect calibration compositions and methods are also disclosed. The described methods, systems, and devices have primary applications in combinatorial polymer research and in industrial process control.

Abstract: A transparent flow cell is used as an index-guided optical waveguide. A detector for the flow cell but not the liquid stream detects the Right-Angle-Scattered (RAS) Light exiting from one end of the flow cell. The detector(s) could view the trapped RAS light from the flow cell either directly or through intermediate optical light guides. If the light exits one end of the flow cell, then the other end of the flow cell can be given a high-reflectivity coating to approximately double the amount of light collected. This system is more robust in its alignment than the traditional flow cytometry systems which use imaging optics, such as microscope objectives.

Abstract: A particle measuring apparatus includes a characteristic parameter extracting device for extracting a plurality of characteristic parameters from each particle in a sample, and a distribution diagram preparing device for preparing a first distribution diagram on the basis of the extracted characteristic parameters. It further includes a first separating device for separating a cluster including target particles from others on the prepared first distribution diagram. In addition, a discriminating device is included for setting a specified discrimination standard for the separated cluster including the target particles and for judging whether the particles in the cluster are target particles or non-target particles on the basis of the discrimination standard. Finally, a counting device is included for counting the number of the target particles on the basis of a discrimination result of the discriminating device.

Abstract: An apparatus for measuring fallout of particles on a surface of the type using a telltale plate which is exposed for a particular time period to the fallout of the particles. The apparatus illuminates the telltale plate when it is inserted into the measuring apparatus with the illuminating structure being adapted to emit at least one light beam substantially parallel to the upper surface.

Abstract: A flow cell is provided with a cell body having an inlet flow passage, a detection flow passage, an outlet flow passage, and windows fixed to the cell body on both sides of the detection flow passage. The inlet flow passage is formed by inserting in and closely contacting a tube in and to a hole formed in the cell body, respectively.

Abstract: Particles generated within a semiconductor wafer process chamber are monitored by emitting a rastered laser beam into the process chamber and detecting a two-dimensional image of scattered radiant energy within the process chamber. A video frame representing a matrix array of pixel intensities is produced and processed by a processor. The processor receives first and second video frames, the first frame representing a matrix array of pixels of a background image of the process chamber before a wafer processing is started and the second frame representing a matrix array of corresponding pixels of a target image of the process changer after a wafer processing is started. Differential intensities between the pixels of the background image and corresponding pixels of the target image are detected and a decision is made on the detected intensities to produce an output signal representing presence or absence of the particles.

Abstract: The present invention provides a device for studying particles in a fluid that advantageously allows particles having a broad range of particle size, e.g., in the 3-1000 .mu.m range, to be readily imaged and counted.

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: A method and apparatus for an improved spectral imaging system is provided. The system is capable of measuring the fluorescence, luminescence, or absorption at selected locations on a sample plate. The emissions detection subassembly can tune to any wavelength within a continuum of wavelengths utilizing an interferometric spectral discriminator. The interferometric spectral discriminator creates an interferogram from which the wavelength spectra for each pixel of the array can be calculated, typically using Fourier transform analysis. In one aspect, the chromatic accuracy of the system is calibrated using a calibration slit placed in the input aperture of the input relay lens but outside of the sample image. The slit is illuminated using a source of known wavelength. The fringe count versus the wavelength of the slit illumination source is monitored and used to calibrate the spectral discriminator.

Abstract: A method of fabricating a semiconductor device includes the steps of illuminating a structure formed on a surface of a substrate by an incident optical beam incident to the structure with a predetermined incident angle with respect to the surface, measuring a polarization state of an exiting optical beam exiting from the structure in response to an illumination of the structure by the incident optical beam, and evaluating a size of the structure in a direction parallel to the surface from the polarization state of the exiting optical beam, and adjusting a parameter of production of a semiconductor device in response to the size.

Abstract: An ultra-miniature personal flow cytometer (pFCM) for the measurement of laser-induced fluorescence. The pFCM is approximately the size of a fluorescent microscope and includes a miniature optical module onto which the flow cytometry components are coupled. The miniature optical module is closely integrated with a flow cell through which a sample cell stream flows. The advantage of the pFCM is its compact size and efficiency that is made possible due to the unique microchip demultiplexing waveguide utilized in the separation of fluorescent wavelengths. The microchip demultiplexing waveguide is wholly contained in a tiny microchip consisting of a wave channel layer, a buffer layer, a substrate layer, and a plurality of micrograting filters. Photodetectors may either be coupled to the microchip demultiplexing waveguide by individual fiber optic members or incorporated into the wave channel layer in a photodiode array.

Abstract: A plastics material which contains a pigment composition comprising a pigment having adsorbed on its surface, or as a physical mixture, up to 10% by weight, based on the total weight of pigment composition of a coding compound which is a compound containing azo, azomethine or polycyclic chromophore and which has an absorption spectrum and a Raman spectrum different from that of the pigment.

Abstract: The present invention relates to three-dimensional optical imaging techniques and, more particularly, to the detection and three-dimensional imaging of absorbing and/or scattering structures in complex random media, such as human body tissue, by detecting scattered light emerging from the medium.

Abstract: Method and system for imaging media having spatially varying dynamic properties or spatially varying optical properties. The method and system utilizes a diffuse correlation wave which is a function of the properties of the medium. The correlation is constructed from photons which create a speckle pattern which falls on a detector at a known position with respect to the source of the photons after the photons have interacted with the media.

Abstract: An optical analyzer with a configuration particularly suitable for use with planar liquid sample flow cells is provided comprising a polarized light source and at least two large angle scattered light photodetectors positioned respectively at acute, and right or oblique angles to the incident light beams. Differences in intensities of light measured at the two photodetectors are used to quantify components of the sample.

Abstract: Solid particles combined with a water contaminated oil sample are counted by an optical particle counter. The contaminated oil sample is mixed at a substantially 1:1 ratio with a water masking solvent comprising about one part isopropanol and about three parts toluene. The oil and solvent mixture is passed through a transparent viewing volume between a light source and a light detector for detection and counting of oil suspended solid particles.

Abstract: System for, and method of, monitoring airborne particulate, including particulate of the PM.sub.2.5 class. The system for monitoring airborne particulate includes an optical sensor to measure size characteristics of sampled airborne particulate and a humidity sensor to measure relative humidity. An adjusted airborne concentration value is then produced in response to the measured size characteristics and to the humidity measurement. According to one embodiment the optical sensor is implemented as a multi-wavelength nephelometer, e.g., two-wavelength nephelometer. According to another embodiment the humidity sensor is placed relatively near the optical sensing region and makes a relative humidity measurement.

Abstract: A submersible light scattering probe for the absolute characterization of polymer and colloid solutions includes a ring member made of a preferably dark, opaque material, having embedded therein a plurality of optical fibers which can be connected to optical detectors remote from the probe. The ends of the optical fibers are preferably in direct contact with the fluid being tested. Instead of submersing the probe in a fluid, fluid can be caused to flow through the probe, placed in the probe, or placed in a transparent vessel placed in the probe. Individual large scattering particles can also be detected, counted, and characterized at the same time absolutes characterization of the polymer or colloid solution is performed.

Abstract: A method for monitoring the presence of particles in a plasma etch chamber. It includes the steps of: (a) selecting at least one laser light source whose wavelength is at such an energy which will cause the particles to be monitored inside the plasma etch chamber to emit Raman, Stoke, and anti-Stoke spectra lines when the laser light is scattered by the particle; (b) emitting the laser light into an internal space of the plasma etch chamber; and (c) using a set of fiber optics to intercept light that may be scattered by the particle, if the particle is present in the plasma etch chamber; and (d) measuring amplitude and spectra of the scattered light. Because the intensity of the scattered light is proportional to the dielectric constant to the fourth power, the method is most advantageous for detect the presence of metal-containing particles, which have a very high dielectric constant. The spectral analysis also provides information relating to the chemical composition of the particles.

Abstract: A method for sensing the concentrations of diatomic gases in a flow chamber is achieved by focusing an incident beam of light from a monochromatic light source on a point internal to the flow chamber through a transparent window. The incident excites molecules of the diatomic gas, resulting in emission of scattered light of particular characteristic frequency for each species of diatomic gas, due to the Raman principle. By collecting the scattered light beam from the flow chamber through the window and analyzing the intensity of the collected scattered beam at these characteristic frequencies, the relative concentrations of each of the diatomic gases may be determined.

Abstract: The present invention provides a highly sensitive and accurate method and system for the discrimination and quantification of platelets in a whole blood sample using automated hematology instruments. The method and system of the invention provide the accurate measurements of platelet dry mass and platelet component concentration in both normal blood samples and in abnormal blood samples, such as those from thrombocytopenic patients. The determination of platelet dry mass and platelet component concentration can serve to assess the activation state of platelets since activated platelets possess measurably lower component concentrations and refractive indices than do non-activated platelets. The method and system of the invention also allows the clinician or skilled practitioner to determine the age of a blood sample on the basis of the measured parameter of platelet component concentration.

Abstract: A system is disclosed for the extraction and delivery of a diluted representative sample of a processed medium, flowing as a process stream in a conduit, for the analysis by a particle measurement instrument. The system includes a shroud tube located within the conduit, longitudinally aligned with the process stream and arranged to receive and allow a portion of the process stream to flow therethrough. A diluent delivery apparatus includes an emitter that is located in the shroud tube arranged to release a stream of diluent into the shroud tube. The diluent released by the emitter mixes with the processed medium within the shroud tube. A sample recirculation apparatus is connected to the particle measurement instrument and includes a collector located in the shroud tube downstream from the emitter and a drain located in the conduit downstream of the collector.

Abstract: The present invention relates to a fiber optic detector for detection of scattered light or fluorescent light from a liquid suspension, comprising: a lighting optical fiber for transmitting light to a lighting optical fiber outlet; a first gradient index lens disposed at the lighting optical fiber outlet to parallelize light; a detecting optical fiber for transmitting back-scattered light from a detecting optical fiber inlet; a second gradient index lens disposed at the detecting optical fiber inlet to parallelize back-scattered light; and at least one means for focusing parallelized light transmitted from the lighting optical fiber on a point and for focusing light back-scattered from the point to the second gradient index lens of the detecting optical fiber for transmission by the detecting optical fiber.

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 laser is irradiated on the surface of a semiconductor wafer while a stage mounted on the semiconductor wafer is moved, and scattering lights emitted from the surface of the semiconductor wafer is received by the receiving device, and an intensity distribution of the scattering lights is measured. The intensity distribution is processed by the controller so as to obtain a defect density of the semiconductor wafer.

Abstract: A method and an apparatus for determining the coverage of the interface between a liquid first phase and a liquid or gaseous second phase by at least one molecular species, at least the following procedural steps being carried out successively: the generation of a stream of droplets which contain at least the liquid first phase, in such a way that the droplets move along a droplet trajectory, and the non-contact determination of a measure of the coverage of the interface by the at least one molecular species at at least two different points along the droplet trajectory.

Abstract: A system (10, 110, 210) for detecting particles (144) on a surface of a substrate-supporting chuck (14, 114, 214) including an inspection subsystem (128, 130, 131, 116, 250, 252, 222, 216) for analyzing the surface of the chuck (14, 114, 214) to determine if any particles (144) are thereon, a movable table (16, 116, 216) for holding the chuck (14, 114, 214) to inspect it and for moving the chuck (14, 114, 214) during inspection, and a control unit (22, 122, 222) for moving the movable table (16, 116, 216) relative to the inspection subsystem (128, 130, 131, 116, 250, 252, 222, 216) to inspect the surface of the chuck (14, 114, 214) and to produce an indication signal if a particle (144) is detected on the surface of the chuck (14, 114, 214).

Abstract: Disclosed herein is a method and an apparatus for applying a coating liquid to an object from a liquid-applying member at a first prescribed position, thereby forming a film on the object. Before the coating liquid at the first position, the coating liquid is applied at a second predetermined position. An impurity-detecting device detects the impurities contained in the coating liquid applied at the second position. A particle-counting device is provided, and a switching device is provided on a liquid-supplying pipe extending from a source of the coating liquid to the liquid-applying member. The switching device switches the supply of the coating liquid between the liquid-applying member and the impurity-detecting device. The impurities in the coating liquid can thereby monitored.

Abstract: A method for optically inspecting a semiconductor substrate for defects such as oxidation induced stacking faults, and a template mask which assists in practicing the optical inspection method. There is first provided a semiconductor substrate which has a surface to be inspected for defects such as oxidation induced stacking faults. Aligned then upon the surface of the semiconductor substrate to be inspected for defects such as oxidation induced stacking faults is a template mask. The template mask has a minimum of one aperture which leaves exposed a portion of the surface of the semiconductor substrate to be inspected for defects such as oxidation induced stacking faults. Finally, there is inspected optically the portion of the surface of the semiconductor substrate exposed through the aperture.

Abstract: An autocollimator/point-range sensor system produces a linearly polarized light beam that is split into a point-range sensor beam and an autocollimator beam. The linearly polarized point-range sensor beam is utilized to carry out z-position measurements according to prior-art techniques. The autocollimator beam is passed through a quarter-wave plate to introduce a 90-degree phase shift and convert it to circularly polarized light. An analyzer placed in front of the autocollimator detector is positioned such that its transmission axis is offset with respect to the plane of polarization of the linearly polarized point-range sensor beam, thereby blocking any scattered light from the sensor beam while passing a component of the circularly-polarized autocollimator light to reach the detector.