Device for measuring three-dimensional velocity, size, and/or shape of particles

Inventors

Nowicki, KeithParker, AlexSoto, Alejandro

Assignees

Southwest Research Institute SwRI

Publication Number

US-12078584-B2

Publication Date

2024-09-03

Expiration Date

2041-12-10

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Abstract

A velocimeter/nephelometer for measuring the three-dimensional velocity and/or size and/or shape of a particle. A set of laser interferometers and a set of photodiode detectors are arranged on a two-dimensional platform. Each laser interferometer produces a laser beam, with the beams intersecting within an inner area of the platform. Two of the laser interferometers produce like-oriented fringe patterns with an angular separation between the propagation direction of their beams of ninety degrees. A third of the laser interferometers produces a beam with the fringe pattern oriented orthogonal to the fringe patterns of the other two laser interferometers. Each detector is positioned and filtered to detect light from an associated laser interferometer, the light having been scattered by a particle as the particle passes through a volume of observation.

Core Innovation

The invention is a compact, low-mass, diode-laser-based device, termed a laser velocimeter/nephelometer (LVN), for measuring the three-dimensional velocity, size, and shape of particles in free space. The LVN consists of a set of three laser interferometers and associated photodiode detectors, all arranged on a two-dimensional platform. Each laser interferometer produces a laser beam with a fringe pattern; these beams intersect within a defined observation volume, allowing for spatially precise measurements.

Two of the laser interferometers are oriented such that their beams intersect at ninety degrees with like-oriented fringe patterns, while a third produces a beam with fringe orientation orthogonal to the first two. Each detector is specifically filtered and positioned to detect only light emanating from its associated laser interferometer after scattering by particles passing through the observation volume. This arrangement enables measurement of all three orthogonal velocity components (x, y, and z) using linear interference fringe encoding and spectral isolation for each velocity component.

Measurement of particle size and shape is achieved by detecting Mie scattering using the intensity and spatial distribution of forward-scattered light at several locations, with each interferometer beam providing a different wavelength. Data from the detectors is processed to yield three-dimensional information on velocity, size, and shape by leveraging the high intensity of forward-scattered light and by applying Fourier analysis techniques. The device addresses the problem of measuring three-dimensional particle characteristics with greater compactness, exploiting orthogonal fringe patterns and multiple wavelengths in a two-dimensional structure.

Claims Coverage

The patent contains two independent claims covering two inventive features.

Velocimeter/nephelometer device with intersecting laser interferometers and filtered detectors

The device comprises: - A two-dimensional platform supporting three laser interferometers. - Each interferometer produces a laser beam with a fringe pattern. - The beams intersect within an internal observation volume. - Two beams are spaced ninety degrees apart with like-oriented fringe patterns and propagation directions separated by ninety degrees. - The third beam's fringe pattern is orthogonal to the fringe patterns of the first two. - At least three photodiode detectors are mounted on the platform, each positioned and filtered to detect only light from the corresponding interferometer, specifically light scattered by a particle passing through the observation volume.

Method of measuring three-dimensional particle velocity, size, and shape using a compact platform

The method includes: - Collecting a particle in the observation space of a device with a two-dimensional platform and three laser interferometers (as specified above), where the beams intersect within a volume of observation. - Arranging two interferometers at ninety degrees apart with like-oriented fringe patterns and a third with an orthogonal fringe pattern. - Positioning and filtering at least three photodiode detectors to collect scattered light from an associated interferometer as a particle passes through the observation volume. - Processing the outputs of the detectors to produce data representing the three-dimensional velocity, shape, and/or size of the particle.

The inventive features cover both the device structure and its method of operation, enabling three-dimensional measurements of particle velocity, size, and shape using specific beam geometries and filtered detection.

Stated Advantages

The LVN enables three-dimensional velocity, size, and shape measurements of particles using a compact two-dimensional platform.

The use of forward-scattered light, which has much higher intensity than backscattered light, reduces the required collection cross-section of the detector.

The entire beam length can be used to acquire velocity data, not restricting measurements to a small intersection volume.

Multiple wavelengths provide unique measurements of particle size and enhance the accuracy of size and shape determination.

Documented Applications

Measuring particle velocity, size, and shape in free space.

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