LASER DOPPLER VELOCITY METER Russian patent published in 2019 - IPC G01P5/26 

FIELD: measuring equipment.

SUBSTANCE: present invention relates to measurement equipment and can be used in experimental hydro- and aerodynamics, in industrial technologies associated with the need to study velocities of flows of gas and condensed media, as well as speed of surfaces. Laser Doppler velocity meter comprises series-arranged bi-chromatic source of two spatially aligned orthogonally polarized laser beams with wavelengths λ_r and λ_g, first lens, acousto-optic Bragg traveling wave modulator, a second lens, an achromatic half-wave phase plate placed on the path of one of the diffracted beams, a polarization prism of Wollaston, located in the image plane of the source of the beams diffracted in the acousto-optic modulator. Speed meter also includes third lens, front focal plane of which is combined with plane of splitting of beams in polarization prism of Wollaston, half-wave phase plates on paths of two Wollaston-split beams with wavelengths λ_r and λ_g, fourth lens – probing optical field shaper in analyzed medium, rotary mirror installed between third and fourth lenses, mounted on path of light beam from monochromatic pair with wavelength λ_g beam splitting plate oriented at Brewster angle, and in series with it quarter-wave plate, in the path reflected by the beam-splitting beam of beams, there are successively installed quarter-wave phase plate and mirror, on path of light beam scattered in direction of incident wave with wavelength λ_r and reflected from the beam splitting plate, sequentially installed optical filter at wavelength λ_r and a photodetector connected through an analogue-to-digital converter to a signal processing system. At that, Bragg acousto-optic modulator is made as two-wave modulator with frequency ratio Ω_r and Ω_g of ultrasonic waves equal to ratio of wave numbers k_r and k_g diffracting light beams, and photodetector installed on path reflected by mirror of light field scattered by investigated medium is connected to signal processing system through band-pass filters, central frequencies of which are equal to frequencies Ω_r and Ω_g ultrasound waves in acousto-optic modulator.

EFFECT: high accuracy of measuring speed.

1 cl, 8 dwg