Hewlett-packard Company

Siegen Corporation

Optoscan Corporation

David A Blau

William R Fish

Michael W Leitner

William G Divens

William B Cole

A gas chromatography plus mass spectrometer (GC/MS) system includes a gas chromatograph, a mass spectrometer, and a computer interface to both of them. The mass spectrometer includes an ion source with an electron emission filament which can be damaged if on during the time a solvent peak is eluting from the chromatography. The filament is regulated to provide a constant emission rate by feedback which causes a current source to compensate deviations from a desired emission level. When a solvent peak begins to elute, the concomitant sudden cooling of the filament is sensitively reflected in the feedback to the current source. a comparator AC-coupled to the current source input can be used in shutting off the current source when the emission current abruptly drops. A computer controller can reactivate the filament in response to a decrease in ambient pressure or elapse of a predetermined duration so that component peaks following the solvent peak can be analyzed.

Electron-emission filament cutoff for gas chromatography + mass

Disclosed is a preamplifier which is responsive to a physiological potential developed by a subject and operative to develop a potential suitably isolated therefrom, the preamplifier including a pair of input networks for receiving therebetween the physiological potential, a pair of operational amplifiers each connected in a unity (voltage) gain, voltage follower, configuration and each driven by a respective one of the input networks, a low resistance resistor connected between the voltage followers to directly develop from the potential a current of suitable level for directly driving an optical isolator, and an optical isolator having an input portion which is connected in the feedback path of one of the operational amplifiers so as to be driven by the current and an output portion at which the optical isolator develops the isolated potential.

Physiological potential preamplifier

An optical system and associated electronic processing for measuring 0.5-micron and larger dimensions on sample wafers by transversely moving the sample under a stationary microspot provided by a tightly-focused ultraviolet ('UV') laser beam and detecting the interaction of the laser microspot with the sample. The optical system includes a high numerical aperture objective close to the sample surface, a first UV optical train, a second UV optical train, and a UV detector. The first train transports the laser beam to the objective for focusing at the sample surface. The second train communicates UV light emanating from the surface and passing through the objective to the UV detector. The second optical train preferably includes a pinhole which provides added spatial resolution, both laterally and vertically. Light emanating from scattering centers laterally away from the spot or from deeper layers within the wafer focus at different points and are blocked by the edges of the pinhole.

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Los Altos, CA, United States of America

David A Blau