| 摘要 |
In the method, a volume (5) to be measured is illuminated by a pair of light beams (3) which cross each other. The Doppler-shifted scattered light (8) originating from the particles (6) which are moved along with the flow is registered and converted into electric signals (1). The Doppler frequency of the registered scattered light (8) is used as a measure of the flow velocity. The electric signals (1) of the registered scattered light (8) are digitized and represented in the form of an image and a coherent light beam is transmitted through the image. The coherent light beam (14) is focussed in a Fourier plane (18) as a result of which a Fourier-transformed image (22) of the electric signals (1), which exhibits a dot pattern (24), is generated. The Fourier-transformed image (20) is recorded and processed further. The device for carrying out the method exhibits a light source (2), a first optical system (4) which focusses the light beam (3) in the volume ( 5) to be measured and picks up the scattered light (8), a converter unit (9) which converts the registered scattered light (8) into electric signals (1), and an evaluating unit which further processes the electric signals (1) and represents them as velocities. The evaluating unit is associated with a controllable light modulator (13) through which the coherent light beam (14) is transmitted for displaying the electric signals (1) of the registered scattered light (8). A second optical system (17) is provided which focusses the coherent light beam (14) in the Fourier plane (18). An optical sensor (19) imaging the Fourier-transformed image (20) is provided in the Fourier plane (18). An evaluating processor (22) is arranged which records and further processes the output signals (21) of the optical sensor (19).
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