Tsi, Inc.

Powerscope Incorporated

Amir A Naqwi

Leslie M Jenson

Christopher W Fandrey

Size distribution of elongated objects is measured by forward scattering radiation from the objects at a range of scatter angles. The scattered radiation is refracted to locations on a scatter detector based on the scatter angles and independent of the location of the objects along the radiation axis. The intensity of radiation is sensed at each position on the scatter detector, and signals representative of the intensities at the positions are processed and compared to masks to identify a size distribution. The scatter detector may include individual radiation detectors arranged to receive refracted radiation representing respective ranges of scatter angles to thereby compensate for lower radiation intensities scattered from smaller objects.

Laser diffraction process and apparatus for width measurement of elongated objects

A device and process for interferometric sizing of stochastic (irregular and/or inhomogeneous) particles is disclosed. The device generates a pair of laser beams that interfere with one another to form a measuring volume including interference fringes. Particles crossing the fringes scatter light collected by two or more optical receivers. Outputs of the optical receivers are provided to signal processing and phase processing circuits, to generate indications of particle velocities based on signal frequencies, and indications of particle sizes based on phase shift values. Particles are characterized as to size by generating probability density functions of phase, based on multiple particle traverses through the measuring region, thus to more accurately measure groups of particles, despite the lack of reliability inherent in measuring a single particle. The device is operable in a calibration mode, using particles of known sizes or size distributions. In the calibration mode, phase processing circuitry uses the known particle size distributions and the measured phase distributions to determine certain coefficients which are stored in the phase processing circuitry. These coefficients are later used to generate size distribution functions, based on phase distribution functions obtained by measuring multiple phase values generated by stochastic particles of unknown size.

Non-contact interferometric sizing of stochastic particles

An apparatus for non-contact measurement of particles, fibers and other light scattering elements includes two laser beams that intersect one another to form a measuring region within a composite flow. Particles in the flow scatter the laser energy as they traverse the measuring region. Scattered energy is received by a pair of optical detectors that generate respective electrical signals based on received energy. The detectors have selectively contoured non-rectangular apertures to controllably vary transmittance and as a result generate phase differences according to a corresponding non-linear function that relates the phase differences to particle diameters. One particularly effective aperture shape includes opposite sides contoured according to a lognormal function, to resemble an onion or tear drop. Triangular and trapezoidal apertures also can be used to achieve non-linear functions. In alternative embodiments, rectangular apertures are used in combination with energy attenuation filters with selective gradients in thickness or transmissivity. The result is a selected variance of transmittance in the detector similar to that achieved by controlling the aperture shape.

Device and process for interferometric sizing of particles using spatial

An interferometric system for measuring cross-sectional dimensions of glass fibers and other elongate objects includes: a transmitting optics module for generating two laser beams, and causing the laser beams to intersect and interfere with one another over a measuring volume; several photodetectors to collect the light scattered by the glass fiber positioned in the interference region; and signal processing circuitry to deduce the fiber diameter using phase shifts between the signal pairs and fiber velocity using the frequency of the signals. The system further offers: elimination of the 360.degree. limitation on the product of sensitivity (degrees per micron) and range (microns), accompanied by an increase in accuracy using three or more detectors; uniform sensitivity over a large measuring volume, using fringe flare to compensate for changes in the effective angular separation of the detectors, due to fiber displacement within the measuring volume; and insensitivity to fiber tilt using large-area detectors for receiving the light scattered by the fiber.

Device for interferometric measurements with compensation for tilt and

A system for measuring cross sectional diameters of optical fibers and other elongate cylindrical objects includes a transmitting optics module for generating two collimated laser beams, and causing the beams to intersect and interfere with one another over a measurement region. The optical fiber under inspection is caused to intersect the measurement region with its longitudinal axis perpendicular to a plane defined by the laser beams. Several photodetectors collect light scattered by the optical fiber, and generate signals indicating fiber diameter based on phase differences in the scattered light received by the detectors. The system can determine fiber refractive index by using three detectors to obtain two phase shifts. Differences in Doppler frequencies also are sensed by the detectors, for determining transverse velocity components.

Interferometric device for determining sizes and properties of

A system for measuring cross sectional diameters of optical fibers and other elongate cylindrical objects includes a transmitting optics module for generating two collimated laser beams, and causing the beams to intersect and interfere with one another over a measurement region. The optical fiber under inspection is caused to intersect the measurement region with its longitudinal axis perpendicular to a plane defined by the laser beams. Several photodetectors collect light scattered by the optical fiber, and generate signals indicating fiber diameter based on phase differences in the scattered light received by the detectors. Differences in Doppler frequencies also are sensed by the detectors, for determining transverse velocity components.

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Shoreview, MN, United States of America

Amir A Naqwi