Aerodyne Research, Inc.

Environmental Research & Technology, Inc.

Paul L Kebabian

Kurt D Annen

Henry H Blau, Jr

David B Stickler

Mark Stuart Zahniser

Richard N Jorgenson

Michael Agnese

Andrew Freedman

William Brown

James Assif

Zhenhong Yu

In one embodiment, a return flux linear alternator employs a magnet assembly that includes a pair of permanent ring magnets with opposing polarity and a pair of air gaps. The additional permanent ring and air gap complete a magnetic flux loop of the alternator rather than the magnet pole, as in traditional designs. An alternator coil assembly includes a pair of oppositely wound coil sections that each linearly move through a respective one of the pair of air gaps. In addition, the return flux linear alternator may employ a variety of structures to increase mechanical strength, including a reinforcement fabric, and a variety of structures to increase electrical efficiency, including a thermally conductive but electrically nonconductive spacer between the coil sections and multiple pairs of electrical leads.

Lightweight return flux alternator

In one embodiment, a photoacoustic effect measurement instrument for measuring a species (e.g., a species of PM) in a gas employs a pair of differential acoustic cells including a sample cell that receives sample gas including the species, and a reference cell that receives a filtered version of the sample gas from which the species has been substantially removed. An excitation light source provides an amplitude modulated beam to each of the acoustic cells. An array of multiple microphones is mounted to each of the differential acoustic cells, and measures an acoustic wave generated in the respective acoustic cell by absorption of light by sample gas therein to produce a respective signal. The microphones are isolated from sample gas internal to the acoustic cell by a film. A preamplifier determines a differential signal and a controller calculates concentration of the species based on the differential signal.

Apparatus and methods for photoacoustic measurement of light absorption of particulate and gaseous species

This invention provides a coil and magnet assembly that is operatively interconnected with an oscillating free piston that moves along an axis. A coil mounting disk is operatively connected to a coil assembly. A magnet assembly is mounted on a magnet base. The magnet assembly is coaxial with respect to the coil assembly. The coil assembly and the magnet assembly are in oscillating motion with respect to each other in conjunction with oscillating motion of the free piston. A spring assembly comprising a plurality springs, symmetrically positioned about the axis, extend between the magnet base and the coil mounting disk, so as to move in conjunction with the oscillating motion along the axis. At least some of the springs are conductive and electrically connect the mounting disk to the magnet base. The piston can reside in a casing that is part of either a two-stroke engine or a fluid pump.

Free piston pump and miniature internal combustion engine

In one embodiment, a frequency generator produces an excitation signal, a local oscillator signal, and a reference signal at a difference frequency of the excitation signal and local oscillator signal. The excitation signal is applied to a physical system to produce a response signal, which is mixed with the local oscillator signal. A filter selects a difference frequency component. The frequencies of the excitation signal and/or local oscillator signal are varied, such that the magnitude of the difference frequency is constant, but a sign of the difference frequency changes from positive to negative. The phase shift of the difference frequency component, with respect to the reference signal, at each of the two signs of the difference frequency, is measured. The measured phase shift at the negative sign is subtracted from the measured phase shift at the positive sign, and the difference is divided in half, to produce a result.

System and method for precision phase shift measurement

This invention provides a system and method that enables the use of incoherent light sources, such as light emitting diodes, to provide for the detection of gaseous species which exhibit broadband absorption features (e.g., nitrogen dioxide and the halogen gases). The light emitting diode (LED) is an ideal light source for such an arrangement in that it can be modulated at high frequencies (allowing for omission of external modulation equipment) and provides sufficient illumination within a reasonably narrow wavelength band as compared to, for instance, an incandescent light source. A further advantage of a LED as a light source compared to alternatives such as a gas discharge or arc lamp is that the light output of the LED is highly stable, limited by the stability of the current source used to drive it. Use of a confocal or near-confocal resonant optical cavity maximizes coupling of the light source to the cavity.

System and method for trace species detection using cavity attenuated phase shift spectroscopy with an incoherent light source

The invention provides methods and apparatus for encoding information pertaining to the polarimetric state of transversely propagated radiation&mdash;for example, electromagnetic waves&mdash;as a modulation of the radiation's frequency power spectrum. In a preferred embodiment, suitable for examining light, the radiation passes consecutively through two birefringent media, each having mutually perpendicular fast and slow axes both perpendicular to the propagation axis. The fast axis of the first medium is rotated with respect the fast axis of the second medium to form an acute angle therebetween. The output of the second birefringent medium comprises a complementary pair of interference fringe systems. The power spectrum of each interference system is modulated in a manner characteristic of the polarization state of the radiation. One of the systems is selected by a linear polarizer. The invention is suitable for use in conjunction with a conventional imaging spectrograph and detector.

Polarimetric spectral intensity modulation spectropolarimeter

A miniature, two cycle engine with a linear electrical generator is presented. The piston attaches to the spring and a moving coil is also attached to the spring and/or rod assembly distal from the cylinder head. The spring is formed with an integral end fitting from one piece of preferably titanium stock. A permanent magnet is arranged where the coil moves within the magnet air gap to produce electrical power. The system operates at the resonant frequency of the spring and active mass. A glow plug provides the ignition source and hydrocarbon fuel is used. The package is about an inch wide and about 2-3 inches long, and it weighs about 30 grams.

Miniature generator

A gas-correlation filter spectroscopy-based method and apparatus for determining the concentration of gas species having significant average broadband absorption incorporates a compensating filter having an absorption spectrum that varies with wavelength similarly to the spectrum of the gas species. The compensating filter eliminates interference due to differential absorption. The invention is especially suited to detecting nitrogen dioxide.

Nondispersive optical monitor for nitrogen-oxygen compounds

A system for measuring and monitoring water vapor concentration in a sample uses as a light source an argon discharge lamp, which inherently emits light with a spectral line that is close to a water vapor absorption line. In a preferred embodiment, the argon line is split by a magnetic field parallel to the direction of light propagation from the lamp into sets of components of downshifted and upshifted frequencies of approximately 1575 Gauss. The downshifted components are centered on a water vapor absorption line and are thus readily absorbed by water vapor in the sample; the upshifted components are moved away from that absorption line and are minimally absorbed. A polarization modulator alternately selects the upshifted components or downshifted components and passes the selected components to the sample. After transmission through the sample, the transmitted intensity of a component of the argon line varies as a result of absorption by the water vapor. The system then determines the concentration of water vapor in the sample based on differences in the transmitted intensity between the two sets of components. In alternative embodiments alternate selection of sets of components is achieved by selectively reversing the polarity of the magnetic field or by selectively supplying the magnetic field to the emitting plasma.

Optical monitor for water vapor concentration

A system for measuring and monitoring the concentration of oxygen uses as a light source an argon discharge lamp, which inherently emits light with a spectral line that is close to one of oxygen's A-band absorption lines. In a preferred embodiment, the argon line is split into sets of components of shorter and longer wavelengths by a magnetic field of approximately 2000 Gauss that is parallel to the light propagation from the lamp. The longer wavelength components are centered on an absorption line of oxygen and thus readily absorbed, and the shorter wavelength components are moved away from that line and minimally absorbed. A polarization modulator alternately selects the set of the longer wavelength, or upshifted, components or the set of the shorter wavelength, or downshifted, components and passes the selected set to an environment of interest. After transmission over a path through that environment, the transmitted optical flux of the argon line varies as a result of the differential absorption. The system then determines the concentration of oxygen in the environment based on the changes in the transmitted optical flux between the two sets of components. In alternative embodiments modulation is achieved by selectively reversing the polarity of the magnetic field or by selectively supplying the magnetic field to either the emitting plasma of the lamp or the environment of interest.

Optical oxygen concentration monitor

A method and apparatus for detecting fluorescence from sunlit plants is based on spectral line discrimination using the A-band and B-band absorption of atmospheric oxygen. Light from a plant including scattered sunlight and the fluorescence from chlorophyll is passed through a chopper into a cell containing low-pressure, high-purity oxygen. A-band or B-band wavelengths present in the light are absorbed by the oxygen in the cell. When the chopper is closed, the absorbed light is remitted as fluorescence into a detector. The intensity of the fluorescence from the oxygen is proportional to the intensity of fluorescence from the plant.

Spectral line discriminator for passive detection of fluorescence

An off-axis cavity absorption cell (10) includes astigmatic mirrors (22, 28). The cell design is based on a prototype design that yields a closed beam path having a desired geometry, but the mirrors are fabricated so that the ratios of their radii of curvature are actually larger than those calculated for the prototype. To achieve the desired closed beam path, the mirror spacing is adjusted from that of the prototype design, and the planes of their axes of greatest curvature are oriented out of the alignment that characterizes the prototype design. If the mirrors' manufacturing process yields errors in the curvature-radius ratios within certain prescribed limits, a cell of this design can be adjusted to achieve the closed beam path by simply changing the mirror separation and the 'twist angle' between their respective planes of maximum curvature radius.

Off-axis cavity absorption cell

In a laser emitter-receiver system, a tunable diode laser provides a beam of coherent light having a selected frequency. An infrared detector spaced from the source detects the light transmitted along the beam path between the source and the detector and produces a corresponding output in response thereto. A heating laser provides radiation to the diode laser to heat, and thereby to change the frequency of, the latter laser. The radiation from the heating laser is varied periodically to modulate the intensity of the radiation incident on the diode laser thereby to frequency-modulate the diode laser output over a selected tuning range. A controller responsive to the detector output regulates the current to the diode laser to minimize selected frequency components of the modulated light beam from that laser so that the power output of the diode laser varies minimally when that laser is tuned over the selected tuning range.

Method and means for controlling the frequency and power output of a

A detector for a gas analyzer includes a thermal detector, an absorptive film on the surface of said thermal detector, and an enclosure containing a reference gas of the gas species of interest such that the thermal detector is in thermal contact with both the absorptive film and the reference gas. During irradiation, the absorptive film absorbs radiation which passes through the reference gas and causes the thermal detector to generate a corresponding output. When the irradiation is terminated, the heat content of the reference gas, which will be dependent upon the amount of the radiation absorbed, will be communicated to the thermal detector to cause the thermal detector to provide a second output representing the amount of radiation absorbed by the reference gas.

Infrared detector for NDIR gas analysis

A method and apparatus for operating a dual-frequency gas laser so as to controllably switch between frequencies makes use of a cavity so tuned that the comb of resonant frequencies is not commensurate with the frequency difference between the laser operating frequencies, and, in a preferred embodiment, with one of the resonant frequencies tuned to coincide with one of the operating frequencies. The cavity length and overall gain at each frequency are so selected that the spacing between resonant frequencies is greater than the breadth above unity gain of the individual peaks of the gain vs. frequency curve. The active material is subjected to a magnetic field which may be varied in a controlled manner. In a preferred embodiment, this field is applied normal to the optical axis of the resonant cavity, and an optical element within the cavity is arranged to act as a plane polarizer with its plane of polarization normal to the magnetic field.

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Acton, MA, United States of America

Paul L Kebabian