Abstract: System and method are disclosed for inspecting objects, such as sheets of flat panel glass, to detect flaws or contamination at a surface. The surface to be inspected is illuminated with 253.7 nm ultraviolet (UV) radiation to assure detection of defects only at the front surface subjected to the radiation. UV radiation reaching the front surface is scattered by defects at the front surface, and scattered UV radiation is collected by a UV dark field imaging system and directed by the imaging system to a detecting unit, preferably including a charge coupled device (CCD). The detecting unit senses UV radiation scattered at the surface due to defects within a selected size range and provides an output to a processing unit providing an output indicative of the defects sensed within the selected size range.

Abstract: A modular particle detecting device is disclosed for nonintrusive in-situ detection of particles passing through a sensing region. The device is particularly useful for microcontamination control in semiconductor processing environments, and includes, as separate components, a viewing unit and a sensing unit. The viewing unit has a detecting window and heated illuminating and discharge windows for condensation control. A fluid passage connectable to a flow line enables particle-carrying fluid to pass through a sensing region within the passage. The sensing unit has illuminating circuitry for providing light through the illuminating window to the sensing region, and has detecting circuitry to receive, through the detecting window, light scattered at the sensing region to thereby detect particles in fluid then at the sensing region without physical intrusion of the sensing unit into the sensing region.

Abstract: Submicron diameter particle detection utilizing a high density array is disclosed. The high density array, such as a charge coupled device, is utilized to detect light scattered at a sensing region by particles illuminated by a light source, such as a laser source. Charge storage is utilized to buffer each data frame transferred from the high density array and the multiple serial outputs are processed by parallel processing that includes threshold detection and analog-to-digital converting. A micro-computer and associated digital storage receives the digital outputs and provides outputs indicative of submicron particle sizing.

Abstract: A detection device is disclosed for determining particle size from particle effected light scattering in a sensing region illuminated by a laser beam and receiving the particles in a medium, such as air. Background light from molecular scattering is reduced to a level that enables light scattered by particles having a size of at least as low as about 0.1 micron to be sensed in a high background of molecular scattering such as, for example, where molecular scattering can exceed the 0.1 micron particle's scattering by one hundred times.

Abstract: A surface analysis system and method are disclosed for determining particle contamination and/or defects on or below a surface of material. Laser beams having different polarizations are directed to the surface to be analyzed and light scattered from particle contamination and/or defects on or below the surface is collected and detected to provide electrical signals representative thereof. The electrical signals are then processed to provide an output indicative of sensed contamination and/or defects. In the embodiment particularly shown and described, a pair of polarized laser beams, one of which is a "P" polarized laser beam and the other of which is a "S" polarized laser beam, are separately directed to a monitoring region so that the beams impinge at a common point on the surface to be analyzed.

Abstract: A detection device is disclosed for determining particle size from particle effected light scattering in a sensing region receiving the particles in a gas carrier, such as air, and a laser beam to illuminate the sensing region. Background light from molecular scattering is reduced to a level that enables light scattered by particles having a size of at least as low as about 0.1 micron to be sensed in a high background of molecular scattering such as, for example, where molecular scattering can exceed the 0.1 micron particle's scattering by one hundred times. High molecular scattering is generated whenever the gas volume being viewed is large as is required for high flow rates, high molecular density (high pressures), or large gas molecules.

Abstract: A laser device is disclosed having mirror heating to enhance performance of the device by minimizing induced light absorption to thereby improve mirror quality. The mirrors of a laser device are commonly made of a substrate having a coating thereon formed by alternating layers of high and low refractive index materials, normally classified as refractory oxide materials, which materials are susceptible to formation therein of color centers, such as formation of F-centers when exposed to ultraviolet light, which color centers reduce mirror quality due to induced light absorption losses. By heating the mirror, the F-centers are substantially eliminated to thereby improve mirror quality and enhance the longevity of the laser device.

Abstract: A device and method are disclosed for optically detecting particles in a fluid. A fluid passage with transparent walls defining a monitoring volume, or region, is provided, and particles in the fluid are optically detected by directing a laser beam through the fluid in the monitoring region and collecting light scattered by the particles. A capillary is utilized as the fluid passage, and reflections from the walls of the capillary are effectively precluded. The laser beam is directed through the capillary by means of a window at the entrance side and a lens at the collecting side with the air-glass interfaces being outside the depth of view of particle monitoring within the monitoring region. As a result of this arrangement, the amount of scattered light is greatly reduced and a more uniform light signal is achieved which results in better size resolution of particles than has heretofore been achieved.

Abstract: Particle measurement is disclosed utilizing orthogonally polarized components of a laser beam. A laser beam is split into orthogonally polarized components and at least one of the components is thereafter beam shaped to have a modified dimension. The components are then recombined and focused to provide a beam combination that is directed through a particle containing volume where scattering of the components occurs by the particles. With the components superimposed upon one another, a localized volume is created with one beam being contracted to a smaller volume than the other beam with the illumination intensity ratios thereat being either greater or less than unity depending upon the optics selected.

Abstract: A laser having a stabilized external passive cavity is disclosed, with stabilization being effected by modulation of an external mirror positioned along the laser axis. The laser system includes first, second and third spaced mirrors with the second mirror being an output coupler positioned between the first and third mirrors so that an active cavity is defined between the first and second mirrors and a passive cavity is defined between the second and third mirrors. The active cavity feeds, or pumps, the passive cavity which is stabilized by modulation of the third mirror by movement along the laser axis by linear oscillation to Doppler shift the reflected waves within the passive cavity and thereby produce frequencies that do not interfere with the stable modes of the active cavity.

Abstract: An aerosol sampling device and method are disclosed having improved sample flow characteristics. Sample flowing through an inlet nozzle is heated prior to discharge from the nozzle toward a measurement area to maintain sample flow more nearly laminar by compensating for the adiabatic cooling that occurs due to acceleration of flow through the nozzle. In addition, heating of the sample flow prevents condensation which can result with ambient air having a relative humidity of fifty percent. An optical particle measuring apparatus is shown having a generator for providing a laser beam, the path of which is through a measurement area, and an inlet nozzle through which aerosol sample is injected into the measurement area, after heating in accordance with this invention, to allow operation of the laser at a relatively high Q by reducing non-laminar flow characteristics.

Abstract: Method and apparatus for orienting and measuring fibrous particles by conducting longitudinally oriented fibrous particles through a beam of radiation and measuring the radiation scattered in a direction aligned with the length of such particle and, independently, also measuring the amount of radiation scattered transverse to the length of the particle. Preferably, the measurements are accomplished utilizing a sensor having an inactive center portion substantially corresponding to the area of undisturbed beam of radiation, a first photosensitive area in a portion of the sensor aligned with the length of the particles, and a second, independent photosensitive area transverse to the length of the particle. Signals generated by the two photosensitive areas are added to determine the size of the particles, and the ratio between the signals is established to determine the aspect ratio of the particle.

Abstract: Method and apparatus for selecting data wherein the acceptability of the data is a function of a measurable quality, such as duration, of a specific event relative to the current average, or other statistical threshold, of such quality of a number of events. The magnitude of event characteristic is measured and provided as a signal. Deviations from the threshold are provided to an up-down counter in which the threshold is stored and, accordingly, updated. If the event magnitude, as registered in an up-counter, exceeds the updated threshold stored in the up-down counter, a digital comparator indicates this and up counts the up-down counter to the extent the event exceeds the threshold. If the event magnitude is less than the stored threshold, the up-down counter is down-counted an amount corresponding to the difference between the event magnitude and the stored threshold. A currently updated threshold is thus maintained in the up-down counter.