Method and apparatus for measuring flow motions in a fluid
First Claim
1. A method of determining flow motions in a fluid containing light scattering particles, such as for determining blood circulation in superficial blood vessels in a tissue, the method comprising the steps of illuminating the fluid with monochromatic light;
- gathering light scattered by the particles in in the fluid and any adjacent substantially stationary structures from two, at least partially separated but mutually adjacent regions of the illuminated section of the fluid;
transmitting the light gathered from said two regions separately to two different photodetectors, these two photodetectors receiving light scattered at least partially from different particles;
deriving from the respective output signal from each of the photodetectors a respective signal representing the beat frequency components between light components with different frequencies received by the respective photodetector;
subtracting the two signals so derived from the output signals of the respective photodetectors from one another; and
using the resulting signal from this signal subtraction as a measure of flow motions in the fluid.
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Accused Products
Abstract
For determining flow motions in a fluid containing light scattering particles, in particular for determining the blood circulation in the superficial blood vessels in a tissue, a section of the fluid is illuminated with monochromatic light from a laser (1). Light scattered from particles in the fluid and from any surrounding stationary structures is gathered from two, at least partially separated but mutually adjacent regions of the illuminated section of the fluid and transmitted separately to two separate photodetectors (5, 5'"'"'). From the output signal of each photodetector a signal is derived, which contains the beat frequency components resulting from interference between light components received by the photodetector, which have different frequencies due to the Doppler frequency shift of the light scattered by moving particles. The two signals so derived from the output signals of the two photodetectors are subtracted from each other and the signal resulting from this subtraction is used as a measure of flow motions in the fluid.
77 Citations
12 Claims
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1. A method of determining flow motions in a fluid containing light scattering particles, such as for determining blood circulation in superficial blood vessels in a tissue, the method comprising the steps of illuminating the fluid with monochromatic light;
- gathering light scattered by the particles in in the fluid and any adjacent substantially stationary structures from two, at least partially separated but mutually adjacent regions of the illuminated section of the fluid;
transmitting the light gathered from said two regions separately to two different photodetectors, these two photodetectors receiving light scattered at least partially from different particles;
deriving from the respective output signal from each of the photodetectors a respective signal representing the beat frequency components between light components with different frequencies received by the respective photodetector;
subtracting the two signals so derived from the output signals of the respective photodetectors from one another; and
using the resulting signal from this signal subtraction as a measure of flow motions in the fluid. - View Dependent Claims (2, 3, 4)
- gathering light scattered by the particles in in the fluid and any adjacent substantially stationary structures from two, at least partially separated but mutually adjacent regions of the illuminated section of the fluid;
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5. An apparatus for determining flow motions in a fluid containing light scattering particles, such as for determining blood circulation in superficial blood vessels of a tissue, the apparatus comprising a single monochromatic light source;
- means for illuminating the fluid with light from said single monochromatic light source;
two photodetectors;
means for gathering light scattered by particles in the fluid and any adjacent stationary structures separately from two, at least partially separated but mutually adjacent regions of an illuminated section of the fluid and for transmitting light gathered from said two regions separately to said two photodetectors;
respective, separate signal processing circuitry for each of said photodectors coupled to respective outputs thereof and responsive to respective output signals therefrom for deriving from the output signals of the photodetectors signals containing beat frequency components originating from interference between light components of different frequencies received by respective photodetectors; and
a signal subtracting circuit coupled to said respective signal processing circuitries for subtracting output signals from said two signal processing circuitries from one another. - View Dependent Claims (6, 7, 8, 9, 10, 11, 12)
- means for illuminating the fluid with light from said single monochromatic light source;
Specification