Abstract: A method and apparatus for measuring relative humidity including condensing environmental conditions using a circuit with a capacitive humidity sensor and a reference resistor each connected to an input of a switch device and thence a quadrature sampling circuit. A sinusoidal source is first connected to the reference resistor and secondly to the capacitive humidity while a signal ground is first connected to the capacitive humidity sensor and secondly to the reference resistor. This produces a first voltage and a second voltage that are each sampled in quadrature. A complex ratio of the sampled voltages is calculated and converted into a representation of relative humidity.

Abstract: A method and apparatus for measuring relative humidity including condensing environmental conditions using a circuit with a capacitive humidity sensor and a reference resistor each connected to an input of a switch means and thence a quadrature sampling circuit. A sinusoidal source is first connected to the reference resistor and secondly to the capacitive humidity while a signal ground is first connected to the capacitive humidity sensor and secondly to the reference resistor. This produces a first voltage and a second voltage that are each sampled in quadrature. A complex ratio of the sampled voltages is calculated and converted into a representation of relative humidity.

Abstract: A multi-beam tool is disclosed which can perform square, plumb, and level function which may be required in a construction environment. The tool can generate in a preferred embodiment up to five orthogonal beams with two beams being plumb and three beams being leveled. Combinations of two level beams, or a level and a plumb beam in orthogonal arrangement can produce a square alignment set of beams. The tool includes in a preferred arrangement a self-leveling pendulum to which a laser and quad-mirror arrangement is secured. The self-leveling pendulum is dampened in order to allow the tool to settle down and provide alignment after the tool is positioned as desired.

Abstract: A multi-beam tool is disclosed which can perform square, plumb, and level function which may be required in a construction environment. The tool can generate in a preferred embodiment up to five orthogonal beams with two beams being plumb and three beams being leveled. Combinations of two level beams, or a level and a plumb beam in orthogonal arrangement can produce a square alignment set of beams. The tool includes in a preferred arrangement a self-leveling pendulum to which a laser and quad-mirror arrangement is secured. The self-leveling pendulum is dampened in order to allow the tool to settle down and provide alignment after the tool is positioned as desired.

Abstract: A multi-beam tool is disclosed which can perform square, plumb, and level function which may be required in a construction environment. The tool can generate in a preferred embodiment up to five orthogonal beams with two beams being plumb and three beams being leveled. Combinations of two level beams, or a level and a plumb beam in orthogonal arrangement can produce a square alignment set of beams. The tool includes in a preferred arrangement a self-leveling pendulum to which a laser and quad-mirror arrangement is secured. The self-leveling pendulum is dampened in order to allow the tool to settle down and provide alignment after the tool is positioned as desired.

Abstract: A multi-beam tool is disclosed which can perform square, plumb, and level function which may be required in a construction environment. The tool can generate in a preferred embodiment up to five orthogonal beams with two beams being plumb and three beams being leveled. Combinations of two level beams, or a level and a plumb beam in orthogonal arrangement can produce a square alignment set of beams. The tool includes in a preferred arrangement a self-leveling pendulum to which a laser and quad-mirror arrangement is secured. The self-leveling pendulum is damped in order to allow the tool to settle down and provide alignment after the tool is positioned as desired. The quad-mirror, the magnetic damping, and the coiled wire allowing power to be provided to the laser assembly, each separately, and also in combination, provide for a compact tool.

Abstract: A multi-beam tool is disclosed which can perform square, plumb, and level function which may be required in a construction environment. The tool can generate in a preferred embodiment up to five orthogonal beams with two beams being plumb and three beams being leveled. Combinations of two level beams, or a level and a plumb beam in orthogonal arrangement can produce a square alignment set of beams. The tool includes in a preferred arrangement a self-leveling pendulum to which a laser and quad-mirror arrangement is secured. The self-leveling pendulum is damped in order to allow the tool to settle down and provide alignment after the tool is positioned as desired. The quadmirror, the magnetic damping, and the coiled wire allowing power to be provided to the laser assembly, each separately, and also in combination, provide for a compact tool.

Abstract: A breath sensor utilizes optical fibers to detect the flow of a patients respiratory airstream. As it has no conductive or magnetic parts, it can be used on patients within the bore of a magnetic resonance imaging system for simple, safe, and rapid assessment of a patient's breathing.

Abstract: A System for Collecting Weakly Scattered Electromagnetic Radiation is disclosed. The present invention overcomes problems suffered by previous collection systems by providing a reliable and efficient device for intensifying and collecting the scattered radiation generated by laser induced scattering. The present invention employs a laser source which illuminates an unknown gas contained by a long hollow tube having a highly reflective sheathing. The illuminating electromagnetic radiation from the laser is directed along the entire length of the tube and collides with the molecules of the unknown gas in the tube. The collisions cause the emission of weakly scattered electromagnetic radiation that is shifted in reference to the illuminating radiation. The sheathing is sufficiently reflective of the scattered radiation to substantially contain it. An exit is coupled to the long hollow tube in such a way that the scattered radiation may pass from the reflective sheathing and be collected for analysis.

Abstract: Method and apparatus for determining the composition and concentration of gases present in a patient's airway by measurement of the spectrum of Raman scattered light from these gases. The efficiency is improved by collecting Raman scattered light generated outside the collection region. The gases present are assumed to be drawn from a predetermined set of gases with known Raman scattering spectra, and the concentrations are determined by solution of a matrix equation Ac=b, where the c vector components are the unknown concentrations and the b vector components are determined from measurements of the Raman scattering intensifies in a plurality of wavelength or wavenumber intervals. The linear system of equations represented by the matrix equation may be overdetermined and may require solution by non-conventional methods, such as singular value decomposition.

Abstract: A semiconductor laser power build-up system includes a semi-conductor laser. An optical resonance cavity is defined between at least two reflective elements and has an intracavity light beam along an intracavity beam path. A return light beam, which is a portion of the intracavity light beam, is transmitted through one of the reflective elements and is coincident with but oppositely directed relative to the incident beam. The laser is wholly optically locked to the cavity and the intracavity beam passes substantially without loss within the cavity. In a preferred application, a sample is placed in the cavity and a detector is provided to sense chemicals in the sample by, for example, detecting Raman-scattered light. A wavelength-determining element such as a grating or an etalon is preferably in the incident beam path between the laser and the cavity.

Abstract: A fiber optic pressure sensor suitable for use in measuring, for example, arterial blood pressure, is taught. A catheter tip is formed utilizing the phenomena of collision quenching or Foerster energy transfer quenching of fluorescence in order to measure the pressure exerted by the medium in which the sensors are placed. When utilizing a collision-quenching type of sensor, the change in concentration of a quencher is measured, the quencher being enclosed in the sensor tip, which is in hydrodynamic equilibrium with its ambient environment. Foerster-quenching type sensors measure the change in distance between the quencher and the fluorophore, which in turn are caused by pressure changes caused by the ambient environment in which the sensor is placed.

Abstract: Oxygen determination based on luminescence quenching of fluorescent dye is effected by using the frequency output of an offset-phase locked loop to calculate the time constant for the exponential decay of fluorescence. An offset phase angle between a periodic stimulus signal used to excite the dye and a response signal based on fluorescence detection is predetermined to optimize signal-to-noise ratio for a wide range of time constants. An offset-phase locked loop is used to vary the frequency of a periodic stimulus signal until the predetermined phase relationship is established. Where the stimulus and response signals are substantially sinusoidal, the offset phase angle is ideally about 49.3.degree., although substantially optimal performance is achieved using a more conveniently generated 45.degree.. The 45.degree. angle offset can also be used with a square-wave stimulus signal.