Pacific Scientific Company

Holger T Sommer

Charles F Harrison

A particle sensing cell designed to detect the size of particles in a vacuum line for semiconductor processing equipment, a YAG plate is placed adjacent to the vacuum line conduit to define an external laser cavity extending across the conduit between an end face of the YAG plate and a mirror spaced from the end face across the conduit. The YAG plate will generate a laser beam in the shape of a sheet extending across the conduit. A cylindrical lens is positioned adjacent to the mirror to focus light scattered from particles passing through the laser beam on rectilinear photodetector arrays. Pulses generated by the array are applied to pulse amplitude measuring circuitry.

Vacuum line particle detector with slab laser

In a particle detecting instrument, a particle detecting cell comprises a laser plasma tube in combination with a glass prism through which a fluid channel is defined. The glass prism abuts the transmitting end of the laser plasma tube and the end wall of the prism is arranged at the brewster angle with respect to the plasma tube axis. The fluid channel defined in the prism is also arranged at the brewster angle with respect to the laser beam passing through the prism. A mirror is provided on the prism to reflect the light back through the prism into the plasma tube. The mirror is positioned so that the light reflected back into the plasma tube is in phase with the light amplified within the plasma tube. A mount is provided for the mirror to adjust its lateral and angular position. In an alternative embodiment, the plasma tube abuts a glass window pane defining one side wall of a fluid channel to receive a gas entraining particles to be measured.

Particle contamination detection in fluids through the external section

A method and apparatus for detecting particles contained in a liquid sample includes using a nozzle to form the liquid sample into an unconfined stream having substantially flat sides and directing the stream into intersection with a laser beam in the external cavity of a laser, wherein the sides of the stream are oriented at the Brewster angle with respect to the laser beam. Light scattered from the laser beam by particles in the liquid stream as they pass through the laser beam is collected and directed by a lens to a photodetector which, in response to the impinging scattered light, emits signals for counting and measuring the particles contained in the liquid stream.

Light scattering method and apparatus for detecting particles in liquid

In a particle size measuring system with automatic dilution of the sample containing particles to be measured, the sample is diluted with ionized water in a mixing chamber while continuously withdrawing the mixture of the diluent and the sample in a stream from the mixing chamber. The size of the particles in the stream drawn from the mixing chamber are measured. To insure that the particle size distribution in the stream drawn to the mixing chamber is the same as that in the original sample, a stirrer is provided in the mixing chamber which repeatedly is reversed in its direction of rotation with the time intervals between successive reversals being randomly varied. A cleaning system is provided to clean the mixing chamber as well as the measuring cell in which particle sizes are measured.

Particle size measuring system with automatic dilution of sample

In a particle detector, a stream entraining particles to be measured is passed through a laser beam. Light scattered in two different directions from the laser beam by particles are detected by photodetectors and a coincidence circuit detects simultaneous pulses generated by both photodetectors to discriminate against noise and to disable the integration function in baseline control circuits for preamplifiers amplifying the output signals from the photodetectors. In an alternative embodiment arrays of photodetectors are arranged to detect light scattered in different directions from the sample stream. Optics are provided to focus light scattered from different positions in the sample stream upon different photodetectors in each array so that simultaneous particles in the sample stream can be detected.

Particle size measuring system with coincidence detection

A shim for use in defining a fluid passage in a particle detecting fluid cell has a base portion of metal and head portion, defining the fluid passage, which haws a metal core and a covering which is non-corrodible by water and acid. The sides of the covering and the base portion define continuous flat surfaces which are sandwiched between plates defining the other boundaries of the flow passage. The coverings form a fluid tight seal with the plates and the base portions of the shims bear the compressive forces exerted on the shims by the plates.

Particle measuring fluid cell having non-corrodible shims

An apparatus for detecting submicron particles in air includes a saturator for saturating a sample stream of the air with a vapor of a low volatility liquid and a condenser for cooling the vapor to form droplets around the particles to result in particles of a size detectable by an optical detector. Conduits extend through a bath of the liquid in the saturator so that sample streams passing through the conduits are heated by the bath. A flow divider divides a single sample stream at the inlet of the saturator into a plurality of laminar flow streams corresponding in number to the conduits. The condenser is a heat exchanger having a plurality of tubes with funnel-shaped inlet ends positioned over the bath of the saturator, and the tubes are inclined toward their inlet end so that condensed vapor flows back into the bath. A method for detecting particles in various size ranges involves operating the saturator at different temperatures to vary the minimum size particle which can be grown by condensation to a detectable size.

Submicron particle counting enlarging the particles in a condensation

An integrating sphere for detecting particles in an aerosol has a diffuse reflectant interior surface and a plurality of photodetectors. The aerosol passing through aligned ducts which are spaced at the center of the integrating sphere, and a beam of collimated light, such as a laser beam, projects transversely through the aerosol in the space. Particles in the aerosol scatter the light, and the scattered light is detected simultaneously by the photodetectors within the integrating sphere. A coincidence detection circuit is used to detect the number of times scattered light is simultaneously detected by the photodetectors and, thereby, count the number of particles in the aerosol.

Integrating sphere aerosol particle detector

In an air contamination level detector for detecting the degree of contamination of the intake air to an internal combustion engine, a laser beam is directed through the intake air stream and light scattered from particles in the intake air stream are detected by a photodetector to generate a pulse for each particle. Pulses over a given size are used to enable an AND gate to pass high frequency pulses to a counter, which is periodically recycled. The count accumulated in the counter represents the duty cycle of the pulses and the dirtiness of the intake air. When the count in the counter reaches a preselected level, it causes a warning light to be energized to indicate that the intake air has a exceeded a tolerance level.

Excess air contamination level indicator

In an instrument for measuring the size of particles entrained in a fluid stream, photodetectors are mounted on the walls of tubing shaping the flow of the fluid stream through a laser beam. The photodetectors generate electric current pulses in response to scattering of the light which is generated by the particles passing through the laser beam. The pulses generated by the photodetectors provide a measurement of particle size. The photodetectors are mounted either adjacent to the laser beam on the tubing walls or, alternatively, the tubing walls are mirrored above and below the laser beam and the photodetectors are mounted on the tubing walls at right angle bends of the tubing to receive the light reflected from the mirrored surfaces.

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Greenbelt, MD, United States of America

Holger T Sommer