System for measuring velocity field of fluid flow utilizing a laser-doppler spectral image converter

Claim 1

A system for measuring the velocity of a fluid flow field comprising: laser means for generating a monochromatic laser beam; a member for supporting said fluid flow field; a plurality of particles seeded into the fluid flow field and having the property that they flow along therewith; means for directing said laser beam to said fluid flow field in a manner such that a plane of said fluid flow field is illuminated by a light beam of a predetermined thickness and width, the illuminated plane yielding scattering due to those of said particles in the illuminated plane, said scattered light yielding a frequency shift relative to the frequency of said laser beam due to the Doppler effect; optical means positioned outside of the region of said fluid flow field for collecting scattered light therefrom and for producing an image whose frequency spectrum contains two-dimensional velocity field information; detector means responsive to said image for providing a radiation intensity output which corresponds to said image; and an analyzer disposed between the optical means and the detector means and including a frequency-to-intensity converter for converting Doppler frequency shifted frequencies received from the moving particles into intensity variations in said image said analyzer containing a medium including a uniformly dispersed atomic or molecular species the absorption of which varies significantly as a function of frequency over the range of frequency shifts which result from the Doppler effect caused by movement of said particles so that the image intensity in said image is caused to vary by said absorption as a unique function of the velocity of movement of said particles.

Claim 2

A system for measuring the velocity of a fluid flow field comprising: laser means for generating a monochromatic laser beam; a member for supporting said fluid flow field; a plurality of particles seeded into the fluid flow field and having the property that they flow along therewith; means for directing said laser beam to said fluid flow field in a manner such that a plane of said fluid flow field is illuminated by a light beam of a predetermined thickness and width, the illuminated plane yielding scattering due to those of said particles in the illuminated plane, said scattered light yielding a frequency shift relative to the frequency of said laser beam due to the Doppler effect; optical means positioned outside of the region of said fluid flow field for collecting scattered light therefrom and for producing an image whose frequency spectrum contains two-dimensional velocity field information; detector means responsive to said image for providing a radiation intensity output which corresponds to said image; and an analyzer disposed between the optical means and the detector means and including a frequency-to-intensity converter for converting Doppler frequency shifted frequencies received from the moving particles into intensity variations in said image said analyzer containing a medium including a uniformly dispersed atomic or molecular species the absorption of which varies significantly as a function of frequency over the range of frequency shifts which result from the Doppler effect caused by movement of said particles so that the image intensity in said image is caused to vary by said absorption as a unique function of the velocity of movement of said particles.

Claim 15

A device for converting incident radiation of varying predetermined frequencies into a radiation image having an intensity varying in manner corresponding to the variation of said incident radiation frequency; an enclosure having front and rear wall portions; an absorption medium positioned within said enclosure; said enclosure containing a first aperture in said front wall to allow said radiation to be incident on said cell and a second aperture in said rear wall of said enclosure to allow observation of said image; said cell containing a selectively absorbing medium including atomic or molecular species the absorption of which varies significantly as a function of the frequency over the range of said predetermined frequencies so that the image intensity in said image varies as a unique function of the frequency of said incident radiation; and means for controlling the temperature of said cell whereby the absorption curve of said medium can be varied, said absorption medium transmitting radiation of an intensity which varies with the frequency of the light incident thereon.

Claim 16

A device for converting incident radiation of varying predetermined frequencies into a radiation image having an intensity varying in manner corresponding to the variation of said incident radiation frequency; an enclosure having front and rear wall portions; an absorption medium positioned within said enclosure; said enclosure containing a first aperture in said front wall to allow said radiation to be incident on said cell and a second aperture in said rear wall of said enclosure to allow observation of said image; said cell containing a selectively absorbing medium including atomic or molecular species the absorption of which varies significantly as a function of the frequency over the range of said predetermined frequencies so that the image intensity in said image varies as a unique function of the frequency of said incident radiation; and means for controlling the temperature of said cell whereby the absorption curve of said medium can be varied, said absorption medium transmitting radiation of an intensity which varies with the frequency of the light incident thereon.

Claim 23

A system for measuring the velocity of a fluid flow field with a detector positioned at an image of portions of said field comprising laser means for illuminating the field with light of a predetermined frequency; particle means distributed in said field for flowing therewith and for reflecting laser illumination impinging there on a frequencies related to said predetermined frequency by the addition of a component related to the Doppler shift caused by the velocity of movement of said particles; said laser means delivering an expanded beam to the fluid flow field over a plane passing therethrough and having constant thickness; an optical imaging system for collecting laser beam energy is scattered from said particles and directed at an angle to the beam and adapted to image said plane on said detector positioned at the image thereof; a frequency-to-intensity converter disposed in the optical path forming said image for converting Doppler frequency shifted frequencies received from the moving particles into intensity variations in said image; and said converter containing a selectively absorbing medium, including uniformly dispersed atomic or molecular species exhibiting an absorption which varies significantly as a function of the frequency over the range of frequency shifts which result from the Doppler effect caused by movement of said particles so that the image intensity in said image varies as a unique function of the velocity of movement of said particles.

Claim 24

A system for measuring the velocity of a fluid flow field with a detector positioned at an image of portions of said field comprising laser means for illuminating the field with light of a predetermined frequency; particle means distributed in said field for flowing therewith and for reflecting laser illumination impinging there on a frequencies related to said predetermined frequency by the addition of a component related to the Doppler shift caused by the velocity of movement of said particles; said laser means delivering an expanded beam to the fluid flow field over a plane passing therethrough and having constant thickness; an optical imaging system for collecting laser beam energy is scattered from said particles and directed at an angle to the beam and adapted to image said plane on said detector positioned at the image thereof; a frequency-to-intensity converter disposed in the optical path forming said image for converting Doppler frequency shifted frequencies received from the moving particles into intensity variations in said image; and said converter containing a selectively absorbing medium, including uniformly dispersed atomic or molecular species exhibiting an absorption which varies significantly as a function of the frequency over the range of frequency shifts which result from the Doppler effect caused by movement of said particles so that the image intensity in said image varies as a unique function of the velocity of movement of said particles.