DE102005042954A1 - Particle`s velocity profile determining device, has evaluation unit formed with signal processing units such that two-dimensional XY-point in XY-plane and three velocity components for particles are determined at velocity profiles - Google Patents

Abstract

The device has two transmission optics (91, 92) inclined together with respect to their optical axes (22, 25) such that measuring volumes (6, 7) overlie at a sectional measurement area (8) in a preset XYZ-coordination system. A receiving optics (4) is subordinated to a demultiplexing unit (32) associated with the transmission lenses. An evaluation unit (5) is formed with two signal processing units such that two-dimensional XY-point in a XY-plane spanned in the measurement area and three velocity components for particles are determined at velocity profiles. An independent claim is also included for a method for determining velocity profile in a flow according to a principle of a laser-Doppler-anemometry.

Description

The The invention relates to an apparatus and a method for determination of velocity profiles of arbitrarily directed flows the principle of laser Doppler anemometry with two superimposed, fan-shaped interference fringe systems, which are physically distinguishable, with a transmitting optics linear spaced on its optical axis one of two superimposed Interference fringe systems is assigned to existing measuring volume, in the over a receiving optics and a downstream demultiplexing unit from the scattered light of the particles by means of an evaluation unit for Signal processing of burst signal pairs an axis position and a position-related Lateral velocity component of the particle can be determined.

Conventional speed measurement according to the principle of laser Doppler anemometry (LDA) is based on light scattering of particles entrained in a flow on an interference fringe system, which is formed in the intersection volume of two intersecting, coherent laser beams with as parallel interference fringes as possible, ie with as constant a fringe spacing as possible. In the simplest case of two crossing laser beams, only one lateral component v _{x of} the velocity in the x direction of a given xyz coordinate system with a sensor head is registered, the lateral component v _{x being} perpendicular to the optical axis representing the predetermined z axis, ie Bisector of the two laser beams, is located. The laser Doppler anemometry (LDA) is limited to one-dimensional flows, ie laminar flows or weakly turbulent flows with a main flow direction.

One Problem is that complicated flow fields with this conventional Speed measurement can only be determined with great effort can. This is a quasi-point-like Measurement, where mechanical traversal is required, to determine speed profiles.

• 1) A miniature laser-Doppler velocimeter for simultaneous three-velocity component measurements, Meas. Sci. Technol. 15, S. 2075-2082, 2004 beschrieben, wobei die Messung der Axialgeschwindigkeitskomponente v_z durch Überlagerung eines dritten Interferenzstreifensystems durchgeführt wird, wobei dessen optische Achse einen großen Winkel mit den anderen optischen Achsen bilden soll. Dieses erfordert jedoch einen weiteren optischen Zugang zur Messstelle sowie, falls ein Winkel von kleiner als 90° eingestellt gewählt wird, eine entsprechende Koordinatentransformation, was einen hohen Auswerteaufwand darstellt. In den Auswerteeinheiten der meisten herkömmlichen LDR-Sensoren werden Koordinatentransformationen eingesetzt.

In order to determine the velocity profile of complicated flow fields with oblique particle trajectories, the measurement of all three velocity components of a particle in the document is:

• 1) A miniature laser Doppler velocimeter for simultaneous three-velocity component measurements, Meas. Sci. Technol. 15, pp 2075-2082, 2004, wherein the measurement of the axial velocity component v _{z is performed} by superposition of a third interference fringe system, wherein the optical axis is to form a large angle with the other optical axes. However, this requires a further optical access to the measuring point and, if an angle is selected to be set smaller than 90 °, a corresponding coordinate transformation, which is a high evaluation effort. Coordinate transformations are used in the evaluation units of most conventional LDR sensors.

One Problem is that for the determination of the Axialgeschwindigkeitskomponente a second optical Access for the transmission optics is required.

• 2) Measurement of the velocity of blood flow in vivo using a fiber optic catheter and optical mixing spectroscopy, Appl. Opt. 14, S. 189-196, 1975:
• 3) Optical-fiber laser Doppler velocimeter for highresolution measurement of pulsatile blood flows, Appl. Opt. 21, S. 1785-1790, 1982 und
• 4) Self-mixing laser-Doppler velocimetry of liquid flow and blood perfusion in tissue, Appl. Opt. 31, S. 5844, 1992 sind alternativ einsetzbare interferometrische Verfahren, wie Referenz-Laser-Doppler-Anemometrie oder Selfmixing-Effekt-Verfahren beschrieben, bei denen das dopplerverschobene Streulicht eines Teilchens in axialer Richtung meistens mit einer optischen Faser detektiert und mit einem Anteil nicht-dopplerverschobenen Lichts, das direkt von der Strahlungsquelle abgekoppelt wird, überlagert wird.

In the publications:

• 2) Measurement of the velocity of blood flow in vivo using a fiber optic catheter and optical mixing spectroscopy, Appl. Opt. 14, pp. 189-196, 1975:
• 3) Optical fiber laser Doppler velocimeter for highresolution measurement of pulsatile blood flows, Appl. Opt. 21, pp 1785-1790, 1982 and
• 4) Self-mixing laser Doppler velocimetry of liquid flow and blood perfusion in tissue, Appl. Opt. 31, p. 5844, 1992 are alternatively usable interferometric methods, such as reference laser Doppler anemometry or self-mixing effect method described in which the Doppler shifted scattered light of a particle in the axial direction is detected mostly with an optical fiber and with a The proportion of non-Doppler-shifted light that is decoupled directly from the radiation source is superimposed.

One Problem of the mentioned method is that they are with a high component and cost associated. Because here too only a punctiform Measurement is provided, a mechanical traversal is necessary.

• 5) Monochromatic heterodyne fiber-optic profile sensor for spatially resolved velocity measurements with frequency division multiplexing, Applied Optics Vol. 44, No. 13, S. 2501-2510, 2005;
• 6) Laser Doppler velocity profile sensor with submicrometer spatial resolution that employs fiber-optics and a diffractive lens, Applied Optics Vol. 44, No. 12, S. 2274-2280, 2005;
• 7) Fiber-optic distributed velocity sensor for precision measurements in microscopic and macroscopic flows, Proc. 8^th International Symposium on Laser Metrology, Beitrag 030, Merida/Mexiko, 14.-18. Feb. 2005;
• 8) Highly Spatial Resolved Measurements of Turbulent Boundary Layers by a Laser Doppler Velocity Profile Sensor, 12^th International Symposium on Applications of Laser Techniques to Fluid mechanics, paper 22.4, 12.-15. Juli 2004, Lissabon/Portugal;
• 9) Ortsaufgelöste Laser-Doppler-Geschwindigkeitsprofilmessung von Grenzschichtströmungen, Technisches Messen Vol. 70, Issue 02, S. 59, 2003 und
• 10) Boundary layer velocity measurements by a laser Doppler profile sensor with micrometre spatial resolution, Meas. Sci. Technol. 13, S. 1979-1989, 2002 beschrieben, bei denen zwei Interferenzstreifensysteme, eins mit konvergenten und eins mit divergenten fächerförmigen Interferenzstreifen, zu einem Messvolumen überlagert werden. Die Trajektorien der Teilchen sollen senkrecht zur optischen Achse der Sendeoptik des Liniensensors verlaufen, d.h. die Strömung verläuft senkrecht zur optischen Achse, so dass die Axialgeschwindigkeitskomponente gleich Null ist. Durch Auswertung der Dopplerfrequenzen und ihres Verhältnisses lässt sich aus von der Empfangsoptik weitergeleiteten Impulssignalen (engl. burstsignals) nicht nur die erste Lateralgeschwindigkeitskomponente v_x des Teilchens, sondern zusätzlich die axiale lineare, eindimensionale Position z innerhalb des Messvolumens bestimmen. Der Geschwindigkeitsprofilsensor stellt damit definitionsgemäß einen Liniensensor dar, weil mit ihm die auf der optischen Achse eindimensionale Position eines die optische Achse senkrecht querenden Teilchens ermittelbar ist.

A laser Doppler velocity profile sensor for measuring a first lateral velocity component v _x and the axial position z, ie for line measurement of v _x (z), is in the documents:

• 5) Monochromatic heterodyne fiber-optic profile sensor for spatially resolved velocity measurements with frequency division multiplexing, Applied Optics Vol. 13, pp. 2501-2510, 2005;
• 6) Laser Doppler velocity profile sensor with submicrometer spatial resolution that employs fiber optics and a diffractive lens, Applied Optics Vol. 12, pp. 2274-2280, 2005;
• 7) Fiber-optic distributed velocity sensor for precision measurements in microscopic and macroscopic flows, Proc. 8 ^th International Symposium on Laser Metrology, Entry 030, Merida / Mexico, 14.-18. Feb. 2005;
• 8) Highly Spatial Resolved Measurements of Turbulent Boundary Layers by a laser Doppler velocity profile sensor 12 ^th International Symposium on Applications of Laser Techniques to Fluid mechanics, paper 22.4, 12th-15th July 2004, Lisbon / Portugal;
• 9) Spatially resolved laser Doppler velocity profile measurement of boundary layer flows, Technical Measurement Vol. 70, Issue 02, p. 59, 2003 and
• 10) Boundary layer velocity measurements by a laser Doppler profile sensor with micrometre spatial resolution, Meas. Sci. Technol. 13, pp. 1979-1989, 2002, in which two interference fringe systems, one with convergent and one with divergent fan-shaped interference fringes, are superimposed to form a measurement volume. The trajectories of the particles should run perpendicular to the optical axis of the transmission optics of the line sensor, ie, the flow is perpendicular to the optical axis, so that the Axialgeschwindigkeitskomponente is equal to zero. By evaluating the Doppler frequencies and their ratio, not only the first lateral velocity component v _{x of} the particle, but additionally the axial linear, one-dimensional position z within the measurement volume can be determined from pulse signals forwarded by the receiving optics (English: burstsignals). By definition, the velocity profile sensor thus represents a line sensor, because the position of a particle which is one-dimensionally perpendicular to the optical axis and can be determined with it.

One The problem is that the evaluation unit is constructed in this way is that only speed profiles can be obtained if the trajectories of the particles perpendicular to the optical axis of the line sensor are directed. A multi-dimensional determination requires reconstructions, a high adjustment effort and another (vertical) optical Access.

Of the Invention is based on the object, a method and an apparatus for the determination of velocity profiles of particles in arbitrary directed currents specify that are designed so that the speed profile in the form of a planar and three-speed component image of the existing flow sufficient accurate and can be specified extensively without mechanical Ju stierung. Furthermore the evaluation should be simple and inexpensive. From oneself in the flow Moving particles should also determine the direction of their movement can be.

The Invention is solved by the features of claims 1 and 13.

• – zwei Sendeoptiken vorgesehen, die bezüglich ihrer optischen Achsen geneigt zueinander angeordnet sind, wobei die beiden Messvolumen zu einem Schnittmessbereich in einem vorgegebenen XYZ-Koordinatensystem überlagert sind,
• – wobei die Empfangsoptik im Raum um den Schnittmessbereich angeordnet ist, der die den Sendeoptiken zugeordnete Demultiplexingeinheit nachgeordnet ist, und
• – wobei die Auswerteeinheit mit zwei der Demultiplexingeinheit nachgeordneten Signalverarbeitungseinheiten derart ausgebildet ist, dass zumindest sowohl ein zweidimensionaler XY-Ort X₀, Y₀ in der im Schnittmessbe reich aufgespannten XY-Ebene als auch alle drei Geschwindigkeitskomponenten v_X, v_Y, v_Z für die Teilchen (23) zu zugehörigen Geschwindigkeitsprofilen bestimmbar sind.

In the apparatus for determining velocity profiles of arbitrarily directed flows according to the principle of laser Doppler anemometry with two superimposed fan-shaped interference fringes, which are physically distinguishable, wherein a transmitting optics linearly spaced on its optical axis associated with a two superimposed interference fringe systems measuring volume in which an axis position and a position-related lateral velocity component of the particle can be determined by means of an evaluation unit for signal processing of burst signal pairs via a receiving optical system and a downstream demultiplexing unit from the scattered light of the particles;
are according to the characterizing part of patent claim 1

• Two transmitting optics are provided, which are arranged inclined relative to one another with respect to their optical axes, wherein the two measuring volumes are superimposed to form a cutting measuring area in a predetermined XYZ coordinate system,
• - Wherein the receiving optics is arranged in the space around the cutting measuring range, which is arranged downstream of the demultiplexing unit associated with the transmitting optics, and
• - wherein the evaluation unit with two of the demultiplexing downstream signal processing units is designed such that at least both a two-dimensional XY location X ₀ , Y ₀ in the rich in Schnittbe- rich XY plane and all three velocity components v _X , v _Y , v _Z for the particles ( 23 ) can be determined to associated velocity profiles.

The Both transmission optics can in terms of their optical axes arranged orthogonal to each other be.

• – die Lateralgeschwindigkeitskomponente v_Z der Geschwindigkeit v,
• – die Axialgeschwindigkeitskomponenten v_X, v_Y der Geschwindigkeit v und
• – der Durchtrittsort X₀, Y₀ des Teilchens durch die optische Achsen, bestimmt werden,
• – wobei die Bestimmung der Axialgeschwindigkeitskomponenten v_X, v_Y richtungssinnerkennend ist.

For oblique particle trajectories, ie with non-vanishing axial velocity components v _X , v _Y , the burst signal pairs have a frequency change with time (chirp), the period change with time being directly proportional to the axial velocity components v _X , v _Y and for a single particle

• The lateral velocity component v _{Z of} the velocity v,
• The axial velocity components v _X , v _Y the velocity v and
• The passage X ₀ , Y _{0 of} the particle are determined by the optical axes,
• - wherein the determination of the axial velocity components v _X , v _Y direction sense is indicative.

• – zwei Laserdioden unterschiedlicher Wellenlängen λ₁ ≠ λ₂ oder λ₃ ≠ λ₄, wobei λ₁ ≠ λ₂ ≠ λ₃ ≠ λ₄ sind,
• – jeweils eine Konvexlinse,
• – einen dichroitischen Spiegel,
• – eine Konvexlinse,
• – ein Transmissions-Beugungsgitter,
• – zwei achromatische Linsen, die in ihrer Anordnung ein Kepler-Teleskop bilden,
• – wahlweise Blenden, die nur die +1. und –1. Beugungsordnungen durchlassen und alle anderen Beugungsordnungen blockieren, enthalten.

A transmission optics can

• Two laser diodes of different wavelengths λ ₁ ≠ λ ₂ or λ ₃ ≠ λ ₄ , where λ ₁ ≠ λ ₂ ≠ λ ₃ ≠ λ ₄ ,
• Each one convex lens,
• - a dichroic mirror,
• A convex lens,
• A transmission diffraction grating,
• Two achromatic lenses forming a Kepler telescope in their arrangement,
• - optional irises, which are only the +1. and -1. Pass diffraction orders and block all other diffraction orders.

The Receiving optics can be a convex lens or a convex lens system from which optionally a multimode fiber to the demultiplexing unit guided is.

• – wahlweise einen Eingang für die Multimodefaser,
• – eine eingangsseitige Kollimatorlinse,
• – drei dichroitische Spiegel,
• – jeweils vier ausgangsseitige Kollimationslinsen und
• – vier Photodetektoren zur Signalweiterleitung an die Auswerteeinheit.

The receiving optics for the two transmitting optics may be arranged downstream of a demultiplexing unit, which has the following components:

• - optionally an input for the multimode fiber,
• An input-side collimator lens,
• - three dichroic mirrors,
• - Four output side collimating lenses and
• - Four photodetectors for signal forwarding to the evaluation unit.

there are in any case four input channels for four interference fringe systems each provided with two per emitting optics.

The Contains evaluation unit two signal processing units for the two transmission optics, wherein each signal processing unit of a plurality of functional units exists in which the specified course of detection of the time dependence the Doppler frequency and the evaluation, preferably with programmatic Means, e.g. realized in the graphical programming language LabVIEW is done.

each Signal processing unit has two input channels on the input side, the with the demultiplexing unit via other modules can be connected.

• – einem Analog-Digital-Wandler,
• – einem nachgeschalteten Bandpass, wobei die von den Photodetektoren weitergeleiteten Signale zunächst nach Durchgang durch den Analog-Digital-Wandler mit dem Bandpass gefiltert werden, um den Gleichanteil und hochfrequentes Rauschen zu entfernen,
• – einer Hilbert-Transformations-Einheit, in der die Signaleinhüllenden bestimmt werden,
• – einer Amplituden-Normierungseinheit, in der die Signale normiert werden,
• – einer Gaußfitting-Einheit, in der die Einhüllenden mit Gaußfunktionen gefittet werden, um dadurch die Anfangs- und Endzeiten (definiert über die 1/e²-Schwelle) sowie den Zeitpunkt der maximalen Amplitude t_Max zu bestimmen, wobei die Anfangs- und Endzeiten ein Zeitfenster definieren,
• – einer der Amplituden-Normierungseinheit nachgeschalteten FFT-Einheit, in der das Zeitfenster für die Kurzzeit-Fast-Fourier-Transformation (FFT) genutzt wird, wobei zur Berechnung der Periodendauer-Zeit-Funktionen die Kurzzeit-FFT eingesetzt wird, die ein Auswertefenster über die Zeitsignale schiebt,
• – einer Regressions-Einheit, in der an die Periodendauer-Zeit-Funktionen Regressionsgeraden gefitted werden,
• – einer Berechnungseinheit, in der aus den Regressionsgeraden die Messparameter bestimmt werden.

A signal processing unit of the evaluation unit can consist essentially of the following functional units:

• An analog-to-digital converter,
• A downstream bandpass, wherein the signals relayed by the photodetectors are first filtered with the bandpass after passing through the analog to digital converter to remove the DC and high frequency noise,
• A Hilbert transform unit in which the signal envelopes are determined
• An amplitude normalization unit in which the signals are normalized,
• - a Gaußfitting-unit in which the envelopes are gefittet with Gaussian functions, to thereby start and end times (defined by the 1 / e ² threshold) as well as the time of maximum amplitude t _max to be determined, wherein the start and end times define a time window,
• - One of the amplitude normalization unit downstream FFT unit in which the time window for the short-time fast Fourier transform (FFT) is used, wherein the short-term FFT is used to calculate the period duration-time functions, the evaluation window over push the time signals,
• A regression unit in which regression lines are added to the period duration-time functions,
• - A calculation unit in which the measurement parameters are determined from the regression line.

On the output side, the evaluation unit has a functional unit for the coordinate transformation of calculated speed components at the point of passage X ₀ , Y ₀ , wherein the functional unit is in communication with a display and / or output unit in which either the trajectory angle to the Z-axis can be specified as a direction indication of the trajectory of the particle.

The coordinate transformation transformation unit, in which an averaging of the two lateral velocity components v _Z occurs, is designed such that it determines the passage location X ₀ , Y ₀ and the velocity components via the passage location X ₀ , Y ₀ and the local stripe spacings d _{1 there} , d ₂ calculated for the first transmission optics and the local stripe spacings d ₃ , d ₄ for the second transmission optics.

• – Überlagerung von zwei zueinander geneigt angeordneten, jeweils zwei fächerförmigen Interferenzstreifensystemen zweier Sendeoptiken, wobei die fächerförmigen Interferenzstreifensysteme durch Multiplexverfahren physikalisch unterscheidbar und die optischen Achsen geneigt zueinander angeordnet sind,
• – Auswertung der von beiden geneigt zueinander gerichteten, fächerförmigen Interferenzstreifensystemen erhaltenen Dopplerfrequenzen f₁, f₂; f₃, f₄ für eine eindimensionale Positionsbestimmung des Teilchens innerhalb eines Messvolumens aus zwei fächerförmigen Interferenzstreifensystemen,
• – kombinierte Auswertung der von den beiden verschiedenen zueinander geneigten Interferenzstreifensystemen erhaltenen Burstsignalpaare für eine zweidimensionale Ortsbestimmung X, Y in einem Schnittmessbereich der Messvolumen der beiden verschiedenen, zueinander geneigten Interferenzstreifensysteme mittels der Auswerteeinheit und
• – Frequenz-Zeit-Analyse der von den zueinander geneigten Interferenzstreifensystemen erhaltenen Burstsignalpaare zur Bestimmung der beiden in der von den beiden Interferenzstreifensystemen aufgespannten XY-Ebene liegenden Axialgeschwindigkeitskomponenten v_X, v_Y in der Auswerteeinheit.

The inventive method for determining velocity profiles of arbitrarily directed flows according to the principle of laser Doppler anemometry with two superimposed fan-shaped interference fringes, which are physically distinguishable, wherein the transmitting optics linearly spaced on its optical axis associated with the interference fringe systems measurement volume is assigned, in in the characterizing part according to claim 13 has the following steps on a receiving optics and a downstream demultiplexing from the scattered light of the particles by means of an evaluation unit for signal processing an axis position and a position-related lateral velocity component of the particle are determined

• Superposition of two mutually inclined, two fan-shaped interference fringe systems of two transmission optics, wherein the fan-shaped interference fringes are physically distinguishable by multiplexing and the optical axes are arranged inclined to each other,
• - Evaluation of the two inclined to each other, fan-shaped interference fringe systems obtained Doppler frequencies f ₁ , f ₂ ; f ₃ , f ₄ for a one-dimensional position determination of the particle within a measuring volume of two fan-shaped interference fringe systems,
• Combined evaluation of the burst signal pairs obtained from the two different mutually inclined interference fringe systems for a two-dimensional position determination X, Y in a slice measuring range of the measuring volumes of the two different interference fringe systems inclined to one another by means of the evaluation unit and
• Frequency-time analysis of the burst signal pairs obtained from the mutually inclined interference fringe systems for determining the two axial velocity components v _X , v _Y in the evaluation unit lying in the XY plane spanned by the two interference fringe systems.

In the case of orthogonal arrangement of the two interference fringe systems, the velocity components v _X , v _Y lying in the XY plane can be determined without additional transformation computations.

• – zwei überlagerte fächerförmige Interferenzstreifensysteme derart ausgebildet, dass durch Auswertung der von beiden Interferenzstreifensystemen erhaltenen Dopplerfrequenzen f₁, f₂; f₃, f₄ eine Positionsbestimmung innerhalb des Interferenzstreifensystems für eine Ortsbestimmung X, Y der Teilchen durchgeführt wird, wobei
• – durch eine Frequenz-Zeit-Analyse der von beiden Interferenzstreifensystemen erhaltenen Burstsignalpaare in der Auswerteeinheit eine Bestimmung der jeweils zugehörigen Lateralgeschwindigkeitskomponente v_Z und
• – eine richtungssinnempfindliche Messung der Axialgeschwindigkeitskomponenten v_X, v_Y durchgeführt werden.

By means of a transmission optics

• - Two superimposed fan-shaped interference fringes designed such that by evaluating the Doppler frequencies f ₁ , f ₂ obtained from the two interference fringe systems; f ₃ , f ₄ a position determination within the interference fringe system for a position determination X, Y of the particles is performed, wherein
• A determination of the respectively associated lateral velocity component v _Z and by a frequency-time analysis of the burst signal pairs obtained from the two interference fringe systems in the evaluation unit
• A sense-sensitive measurement of the axial velocity components v _X , v _{Y is} performed.

The axial velocity components v _X , v _Y can be determined directly via the temporal change of the period duration time function T (t), wherein the time dependence of the Doppler frequency f ₁ , f ₂ ; f ₃ , f _{4 is} a measure of the ratio between each of an axial velocity component v _X , v _Y and the lateral velocity component v _z , wherein the ratio is given by the respective angle α as an expression of the oblique trajectory of the particle.

The Doppler frequencies f ₁ , f ₂ , f ₃ , f ₄ can both increase and decrease, so that a distinction can be made between a positive and a negative speed component and the axial velocity components v _X , v _{Y are} thus determined in the direction of the interior of the sensor.

A enough size Number of particles can be evaluated by the one prevailing in the cutting volume To determine speed profile.

The determination of the velocity profile in the area of the evaluation unit can be performed with other trans formations, such as the Wigner-Ville transformation, the wavelet transform are performed.

Next the method of wavelength division multiplexing can also other multiplexing methods such as frequency and time division multiplexing or in combination of these.

further developments and specific embodiments of the invention are specified in further subclaims.

The Invention is based on an embodiment closer by means of several drawings explains:

It demonstrate:

1 1 shows an illustration of an apparatus according to the invention for determining velocity profiles of particles in flows with the orthogonal superimposition of two transmission optics, each transmitting optics providing a location coordinate so that the location of a particle in a two-dimensional plane can be determined in the resulting common cutting measurement area,

2 a schematic representation of a line sensor - a spatial coordinate measuring laser Doppler velocity profile sensor - (prior art),

3 a representation of the generation of a converging (bottom) interference fringes system and a superimposed diverging (top) interference fringe system in the crossing region of the laser beams according to the laser Doppler anemometry (prior art),

4 a representation of the basic principle of a line sensor with stripe spacings d ₁ , d ₂ according to 3 and with trajectories of particles moving perpendicular to the z-axis (prior art),

5 a representation of the linear stripe distance functions d ₁ (z), d ₂ (z) - (prior art),

6 a calibration curve q (z) = d ₁ (z) / d ₂ (z) for the determination of the z-position (prior art),

7 a representation of the parameters of the particle movement (prior art),

8th a representation of the detection of the airfoil by the line sensor along a line which lies within a measuring volume on a laminar plate boundary layer (prior art),

9 a schematic representation of a receiving optics and demultiplexing in the event that four different laser wavelengths are used for the production of the four interference fringes,

10 a schematic representation of the evaluation unit with signal processing units, the to the demultiplexing after 9 connected, and

11 a circuit block diagram of a signal processing unit in conjunction with a display of the signals transmitted by the photodetectors of the device according to the invention.

In 1 is the device according to the invention 1 for determining the velocity profile of a particle 23 in flows according to the principle of laser Doppler anemometry, each with two superimposed fan-shaped interference fringes, which are physically distinguishable, each one transmitting optics linearly spaced on its optical axis is assigned a consisting of two superposed interference fringe systems measuring volume, in which a receiving optics the scattered light of the particles by means of an evaluation unit for signal processing, an axis position and a position-related lateral velocity component of the respective particle can be determined represented.

• – Sendeoptiken 91, 92 vorgesehen, die bezüglich ihrer optischen Achsen 22, 25 geneigt zueinander, hier orthogonal in einem vorgegebenen XYZ-Koordinatensystem angeordnet sind, wobei die beiden Messvolumen 6, 7 zu einem Schnittmessbereich 8 überlagert sind, wobei die strömenden Teilchen 23 den Schnittmessbereich 8 beliebig gerichtet durchqueren,
• – wobei die Empfangsoptik 4 beliebig im Raum um den Schnittmessbereich 8 angeordnet ist, der die den Sendeoptiken 91, 92 zugeordnete Demultiplexingeinheit 32 nachgeordnet ist, und
• – wobei die Auswerteeinheit 5 mit zwei der Demultiplexingeinheit 32 nachgeordneten Signalverarbeitungseinheiten 51, 52 derart ausgebildet ist, dass sowohl ein zweidimensionaler XY-Ort X₀, Y₀ in der im Schnittmessbereich 8 aufgespannten XY-Ebene als auch alle drei Geschwindigkeitskomponenten v_X, v_Y, v_Z für die Teilchen 23 zu zugehörigen Geschwindigkeitsprofilen bestimmbar sind.

According to the invention are two

• - Transmission optics 91 . 92 provided with respect to their optical axes 22 . 25 inclined to each other, here are arranged orthogonally in a given XYZ coordinate system, the two measurement volumes 6 . 7 to a cutting range 8th are superimposed, with the flowing particles 23 the cut measuring range 8th traverse in any direction,
• - wherein the receiving optics 4 arbitrary in the space around the cutting measuring range 8th is arranged, the the the transmission optics 91 . 92 associated demultiplexing unit 32 is subordinate, and
• - Where the evaluation unit 5 with two of the demultiplexing unit 32 downstream signal processing units 51 . 52 is formed such that both a two-dimensional XY location X ₀ , Y ₀ in the in the Schnittmessbereich 8th spanned XY plane as well as all three velocity components v _X , v _Y , v _Z for the particles 23 can be determined to associated speed profiles.

• – Überlagerung von zwei zueinander geneigt angeordneten, jeweils zwei fächerförmigen Interferenzstreifensystemen aufweisenden Sendeoptiken 91, 92, wobei die fächerförmigen Interferenzstreifensysteme durch Multiplexverfahren physikalisch unterscheidbar und die optischen Achsen 22, 25 zueinander geneigt angeordnet sind,
• – Auswertung der von beiden geneigt zueinander gerichteten, fächerförmigen Interferenzstreifensystemen erhaltenen Dopplerfrequenzen f₁, f₂ bzw. f₃, f₄ für eine eindimensionale Positionsbestimmung des Teilchens 23 innerhalb eines Messvolumens 6; 7 aus zwei fächerförmigen Interferenzstreifensystemen,
• – kombinierte Auswertung der von den beiden verschiedenen zueinander geneigten Interferenzstreifensystemen erhaltenen Burstsignalpaare für eine zweidimensionale Ortsbestimmung X₀, Y₀ in einem Schnittmessbereich 8 aus den Messvolumen 6, 7 der beiden verschiedenen orthogonalen Interferenzstreifensysteme mittels der Auswerteeinheit 5 und
• – Frequenz-Zeit-Analyse der von den zueinander geneigten Interferenzstreifensystemen erhaltenen Burstsignalpaare zur Bestimmung der in der XY-Ebene liegenden Geschwindigkeitskomponenten v_X, v_Y, v_Z in der Auswerteeinheit 5.

The method for the determination of velocity profiles of particles 23 in flows with two transmission optics 91 . 92 , which are designed according to the principle of laser Doppler anemometry, has the following steps:

• - Overlay of two mutually inclined arranged, each having two fan-shaped interference fringes transmission optics 91 . 92 wherein the fan-shaped interference fringes are physically distinguishable by multiplexing and the optical axes 22 . 25 are arranged inclined to each other,
• - Evaluation of the two inclined to each other, fan-shaped interference fringes Doppler frequencies obtained f ₁ , f ₂ and f ₃ , f ₄ for a one-dimensional position determination of the particle 23 within a measuring volume 6 ; 7 from two fan-shaped interference fringe systems,
• Combined evaluation of the burst signal pairs obtained from the two different mutually inclined interference fringe systems for a two-dimensional position determination X ₀ , Y ₀ in a slice measurement range 8th from the measuring volume 6 . 7 of the two different orthogonal interference fringe systems by means of the evaluation unit 5 and
• Frequency-time analysis of the received from the mutually inclined interference fringe systems burst signal pairs for determining the lying in the XY plane velocity components v _X , v _Y , v _Z in the evaluation 5 ,

• – die zwei überlagerten fächerförmigen Interferenzstreifensysteme derart ausgebildet, dass durch Auswertung der von beiden Interferenzstreifensystemen erhaltenen Dopplerfrequenzen f₁, f₂ bzw. f₃, f₄ eine Positionsbestimmung innerhalb des Interferenzstreifensystems ermöglicht wird,
• – durch eine Frequenz-Zeit-Analyse der von beiden Interferenzstreifensystemen erhaltenen Burstsignale eine Bestimmung der jeweiligen Lateralgeschwindigkeitskomponente und
• – eine richtungssinnempfindliche Messung der Axialgeschwindigkeitskomponente durchgeführt.

It will be

• The two superimposed fan-shaped interference fringe systems are designed such that a position determination within the interference fringe system is made possible by evaluating the Doppler frequencies f ₁ , f ₂ or f ₃ , f ₄ obtained by the two interference fringe systems,
• A determination of the respective lateral velocity component and by a frequency-time analysis of the burst signals obtained from both interference fringe systems
• - Made a direction sensitive measurement of the axial velocity component.

• – zwei Laserdioden 10a, 10b unterschiedlicher Wellenlängen λ₁ ≠ λ₂
• – jeweils eine Konvexlinse 11a, 11b,
• – einen dichroitischen Spiegel 12,
• – eine Konvexlinse 13,
• - ein Transmissions-Beugungsgitter 14,
• – zwei achromatische Linsen 15a, 15b, die in ihrer Anordnung ein Kepler-Teleskop bilden,
• – wahlweise Blenden 16, die nur die +1. und –1. Beugungsordnungen durchlassen und alle anderen Beugungsordnungen blockieren, und einer Empfangsoptik 4, der eine Demultiplexingeinheit 31 zugeordnet ist und die folgende Bestandteile aufweist:
• – eine Konvexlinse 17,
• – wahlweise eine Multimodefaser 20.

In 2 is the construction of a line sensor 2 , also referred to as laser Doppler velocity profile sensor. The line sensor 2 exists according to the prior art according to the document 9) from a transmission optics 9 which contains:

• - two laser diodes 10a . 10b different wavelengths λ ₁ ≠ λ ₂
• - One convex lens each 11a . 11b .
• - a dichroic mirror 12 .
• - a convex lens 13 .
• a transmission diffraction grating 14 .
• - two achromatic lenses 15a . 15b which form a Kepler telescope in their arrangement,
• - Optional irises 16 that only the +1. and -1. Let through diffraction orders and block all other diffraction orders, and a receiving optics 4 , which is a demultiplexing unit 31 is assigned and has the following components:
• - a convex lens 17 .
• - Optionally a multimode fiber 20 ,

• – einen dichroitischen Spiegel 18,
• – Kollimationslinsen 19 und
• – Photodetektoren 21a, 21b.

The demultiplexing unit 31 contains

• - a dichroic mirror 18 .
• - Collimating lenses 19 and
• - photodetectors 21a . 21b ,

The optical axis 22 puts in 1 the Y-axis of the XYZ coordinate system and at the same time the z-direction of a second predetermined xyz coordinate system, wherein in the region of the optical axis 22 the measuring volume 6 located.

The following is the operation within the line sensor 2 according to the prior art according to the document 9) with reference to the xyz coordinate system explained in more detail: The rays of the two laser diodes 10a . 10b each with a convex lens 11a . 11b collimated. With the dichroic mirror 12 , which reflects a wavelength that transmits others, both beams are collinearly superimposed. The convex lens 13 focuses the two beams on the transmission diffraction grating 14 , Of the resulting diffraction orders, the +1. and -1. Beu tion order as the sub-beams for the laser Doppler anemometry selected. The diffraction orders are made with two achromatic lenses 15a . 15b , which form in their arrangement a Kepler telescope, parallelized and brought to overlap. The irises 16 inside the telescope make sure that only the +1. and -1. Diffraction orders are allowed to pass through and all other diffraction orders are blocked. In the intersection of the partial beams, the bichromatic interference fringe system forms, which is the actual measurement volume 6 represents. The flow or the particle direction now form an angle α with that to the optical axis 22 the transmission optics 9 belonging normal direction. That of the flowing particles 23 Scattered light is transmitted through the convex lens 17 into the multimode fiber 20 coupled, which the light to the receiving optics 4 with the downstream demultiplexing unit 31 leads. In the demultiplexing unit 31 that will be the multi-mode fiber 20 leaking bichromatic scattered light 26 first with the collimator lens 19 collimated and then onto the dichroic mirror 18 passed, on which transmits a wavelength, the other is reflected. The two scattered light components 28a . 28b each with a collimator lens 19 on the photodetectors 21a . 21b focused. The photodetectors 21a . 21b conduct the detected signals as a burst signal pair to the evaluation unit 5 further.

The sensor principle is based as in 3 is shown on two superimposed fan-shaped interference fringe systems 61 . 62 that the actual measurement volume 6 form. The interference fringe system 61 the one wavelength λ ₁ has converging, the other wavelength λ ₂ diverging interference fringes 62 on. The fan-shaped interference strip systems 61 . 62 are generated by placing the beam waist of the Gaussian beams used in front of or behind the crossing plane. The axial adjustment of the beam waist is done by individual displacement of the laser diodes 10a . 10b regarding her collimating lenses 11a . 11b ,

The scattered light 26 is detected wavelength selective, each wavelength λ ₁ , λ ₂ forms a channel. It will therefore be of a particle 23 two simultaneous burst signals - a burst signal pair - from the two fringe systems 61 . 62 obtained having different Doppler frequencies f _1.2 .

Since the interference fringe spacings d ₁ (z), d ₂ (z), as in 4 is shown along the optical axis 22 are no longer constant (as in conventional laser Doppler anemometry), the Doppler frequencies f _1,2 = f _1,2 (z) of the two burst signals also depend on the position z along the optical axis 22 from.

Due to the double measurement on both interference fringe systems 61 . 62 This can be exploited to additionally the z-position of a particle 23 to determine. This is done by means of a calibration function q (z), which is formed from the quotients of the two strip spacings d ₁ (z), d ₂ (z):

This is possible because the quotient, as shown, no longer depends on the speed, but only on the z-position. In the 5 . 6 For example, the two measured functions of the interference fringe spacings d ₁ (z), d ₂ (z) and the calibration function q (z) = d ₁ (z) / d ₂ (z) formed therefrom are shown. The functions may vary depending on the adjustment. During a measurement, the two Doppler frequencies are then f ₁ (z), f ₂ is determined (z) and from the ratio thereof on the inverse function z = z (q) determines the z-position. With the determined z-position, the local strip spacings d ₁ (z), d ₂ (z), which were previously determined by a calibration, can be used to calculate the velocity. This results in the first lateral velocity component v _x : v x (z) = f 1 (v x , z) d 1 (z) = f 2 (v x , z) d 2 (z) (II)

In the following, the generalized case is considered that additionally a significant axial velocity component v _{z of} the velocity occurs. The velocity components are then multiplied by the magnitude of the velocity vector v = | v → | and the angle α of the trajectory to the optical axis 22 linked as follows:

The characteristics of equations III, IV, V are given in 7 as representation in the xyz coordinate system supported.

Since the stripe spacings d ₁ (z), d ₂ (z) change with location, as in 7 is shown, the following equations result: d 1 (z) = d 01 + c 1 · zd 2 (z) = d 02 + c 2 · Z (VI, VII) with c _1,2 and d _01,02 as constant parameters. While in 4 the particle 23 moves perpendicular to the optical axis, it deviates according to 7 the movement of the particle 23 in the xz plane of the given xyz coordinate system without the significant second lateral velocity component v _y . Then the trajectory r (t) = [x (t), z (t)] ^T for uniform motion is described as follows: x (t) = v x · Tz (t) = v z · T + z 0 (VIII, IX) wherein the coordinate point z ₀ indicates the z-position at the time t = 0, which is hereinafter referred to as the starting position z ₀ . As a striking, excellent time, the passage through the optical axis 22 can be selected because at this time the highest scattered light intensity, ie the largest signal amplitude occurs. The initial position z ₀ is therefore hereafter defined as the position at which the particle 23 the optical axis 22 crosses.

If equation (IX) is used in equations (VI, VII) and f = v _x / d is taken into account, then for the Doppler frequencies f ₁ (v _x , v _z , z ₀ , t), f ₂ (v _x , v _z , z ₀ , t) are given the following equation:

The Doppler frequencies f ₁ (v _x , v _z , z ₀ , t), f ₂ (v _x , v _z , z ₀ , t) thus become time-dependent as soon as the axial velocity component v _z occurs. The thus existing time dependence of the Doppler frequency forms the basis of the method according to the invention. The time dependence of the Doppler frequency (chirp) can be evaluated by considering the time period T = 1 / f derived from time:

The equation (XI) is temporally constant and directly proportional to the axial velocity component v _z , which is why it can be used to determine it.

• • Die Axialgeschwindigkeitskomponente v_z kann direkt über die zeitliche Änderung der Periodendauer-Zeitfunktion T(t) bestimmt werden. Dabei ist der Chirp – die Zeitabhängigkeit der Dopplerfrequenz – ein Maß für das Verhältnis zwischen Axialgeschwindigkeitskomponente v_z und der ersten Lateralgeschwindigkeitskomponente v_x, wobei das Verhältnis durch den Winkel α als Ausdruck der schrägen Trajektorie der Teilchen 23 vorgegeben ist.
• • Da die Dopplerfrequenz f_1,2(v_x, v_z, z₀, t) sowohl ansteigen als auch abfallen kann, kann zwischen einer positiven und einer negativen Geschwindigkeitskomponente unterschieden werden. Die Bestimmung der Axialgeschwindigkeitskomponente v_z ist somit richtungssinnerkennend.
• • Von einem einzelnen Teilchen 23 können daher folgende Bahngrößen bestimmt werden:
• – die erste Lateralgeschwindigkeitskomponente |v_x|,
• – die Axialgeschwindigkeitskomponente v_z einschließlich des Vorzeichens und
• – die Durchtrittsposition z₀ durch die optische Achse 22.

The following properties can be taken from equation (XI):

• • The axial velocity component v _z can be determined directly via the temporal change of the period duration time function T (t). In this case, the chirp - the time dependence of the Doppler frequency - is a measure of the ratio between the axial velocity component v _z and the first lateral velocity component v _x , wherein the ratio by the angle α as an expression of the oblique trajectory of the particles 23 is predetermined.
• • Since the Doppler frequency f _1,2 (v _x , v _z , z ₀ , t) can both rise and fall, a distinction can be made between a positive and a negative velocity component. The determination of the axial velocity component v _z is thus direction-internal.
• • From a single particle 23 Therefore, the following web sizes can be determined:
• The first lateral velocity component | v _x |,
• - The axial velocity component v _z including the sign and
• - The passage position z ₀ through the optical axis 22 ,

With the line sensor 2 Thus, the velocity components v _x and v _{z are} measured _{as a} function of the z position. Because the particles 23 statistically distributed in the flow needs only a sufficiently large number of particles 23 to be evaluated, in the measuring volume 6 prevailing velocity profile to measure.

In 8th is the velocity profile v _x (z) after a measurement of a laminar plate boundary layer 24 shown. Because the sensor 2 If the velocity profile v _x (z) is missing along a line z, it is called a line sensor.

In the device 1 are in 1 the two transmission optics 91 . 92 with respect to their optical axes 22 . 25 arranged orthogonal to each other. But they can also be inclined to each other or arranged at an angle to each other.

• – die Lateralgeschwindigkeitskomponente v_Z der Geschwindigkeit v,
• – die Axialgeschwindigkeitskomponenten v_X, v_Y der Geschwindigkeit v und
• – der Durchtrittsort X₀, Y₀ des Teilchens 23 durch die optische Achsen 22, 25, bestimmt werden,
• – wobei die Bestimmung der Axialgeschwindigkeitskomponenten v_X, v_Y die Strömungsrichtung der Teilchen 23 angibt.

For oblique particle trajectories, ie, with non-zero axial velocity components v _X , v _Y , the Hurst signal pairs have a frequency change with time, the frequency change with time being directly proportional to the axial velocity components v _X , v _Y , and for a single particle 23

• The lateral velocity component v _{Z of} the velocity v,
• The axial velocity components v _X , v _Y the velocity v and
• - the passage X ₀ , Y _{0 of} the particle 23 through the optical axes 22 . 25 to be determined
• - wherein the determination of the axial velocity components v _X , v _Y, the flow direction of the particles 23 indicates.

• – zwei Laserdioden 10a, 10b unterschiedlicher Wellenlängen λ₁ ≠ λ₂, λ₃ ≠ λ₄, wobei λ₁ ≠ λ₂ ≠ λ₃ ≠ λ₄ ist,
• – jeweils eine Konvexlinse 11a, 11b,
• – einen dichroitischen Spiegel 12,
• – eine Konvexlinse 13,
• – ein Transmissions-Beugungsgitter 14,
• – zwei achromatische Linsen 15a, 15b, die in ihrer Anordnung ein Kepler-Teleskop bilden,
• – wahlweise Blenden 16, die nur die +1. und –1. Beugungsordnungen durchlassen und alle anderen Beugungsordnungen blockieren, enthalten.

The transmission optics 91 . 92 in device 1 are similar and can each

• - two laser diodes 10a . 10b different wavelengths λ ₁ ≠ λ ₂ , λ ₃ ≠ λ ₄ , where λ ₁ ≠ λ ₂ ≠ λ ₃ ≠ λ ₄ ,
• - One convex lens each 11a . 11b .
• - a dichroic mirror 12 .
• - a convex lens 13 .
• A transmission diffraction grating 14 .
• - two achromatic lenses 15a . 15b which form a Kepler telescope in their arrangement,
• - Optional irises 16 that only the +1. and -1. Pass diffraction orders and block all other diffraction orders.

The receiving optics 4 can, as in 9 is shown, a convex lens or a convex lens system 17 included, of the optional multi-mode fiber 20 to the demultiplexing unit 32 is guided.

• – wahlweise einen Eingang für die Multimodefaser 20,
• – eine eingangsseitige Kollimatorlinse 19,
• – drei dichroitische Spiegel 18,
• – jeweils vier ausgangsseitige Kollimationslinsen 19 und
• – vier Photodetektoren 21a, 21b, 21c, 21d zur Signalweiterleitung an die Auswerteeinheit 5.

The receiving optics 4 for the two transmission optics 91 . 92 is the demultiplexing unit 32 is subordinate, comprising the following components:

• - Optionally an input for the multimode fiber 20 .
• - An input-side collimator lens 19 .
• - three dichroic mirrors 18 .
• - Four output side collimating lenses 19 and
• - four photodetectors 21a . 21b . 21c . 21d for signal forwarding to the evaluation unit 5 ,

There are in any case four input channels 53 . 54 . 55 . 56 for four interference fringe systems, each with two per transmission optics 91 . 92 intended.

The evaluation unit 5 in 10 contains two signal processing units 51 . 52 for the two transmission optics 91 . 92 wherein each signal processing unit 51 . 52 consists of several functional units in which the specified course of the detection of the time dependence of the Doppler frequency and the evaluation, which is preferably realized with programmatic means, for example in the graphical programming language LabVIEW, takes place.

Each of the in 10 represented signal processing units 51 . 52 has two input channels on the input side 53 . 54 ; 55 . 56 using the photodetectors 21a . 21b ; 21c . 21d the demultiplexing unit 32 or when using other evaluation methods interconnected assemblies for the formation of two input channels in combination.

• – einem Analog-Digital-Wandler 59,
• – einem nachgeschalteten Bandpass 60, wobei die von den Photodetektoren 21a, 21b; 21c, 21d weitergeleiteten Signale zunächst nach Durchgang durch den Analog-Digital-Wandler 59 mit dem Bandpass 60 gefiltert werden, um den Gleichanteil und hochfrequentes Rauschen zu entfernen,
• – einer Hilbert-Transformations-Einheit 63, in der die Signaleinhüllenden bestimmt werden,
• – einer Amplituden-Normierungseinheit 65, in der die Signale normiert werden,
• – einer Gaußfitting-Einheit 64, in der die Einhüllenden mit Gaußfunktionen gefittet werden, um dadurch die Anfangs- und Endzeiten (definiert über die 1/e²-Schwelle) sowie den Zeitpunkt der maximalen Amplitude t_Max zu bestimmen, wobei die Anfangs- und Endzeiten ein Zeitfenster definieren,
• – einer der Amplituden-Normierungseinheit 65 nachgeschalteten FFT-Einheit 66, in der das Zeitfenster für die Kurzzeit-Fast-Fourier-Transformation (FFT) genutzt wird, wobei zur Berechnung der Periodendauer-Zeit-Funktionen die Kurzzeit-FFT eingesetzt wird, die ein Auswertefenster über die Zeitsignale schiebt,
• – einer Regressions-Einheit 67, in der an die Periodendauer-Zeit-Funktionen Regressionsgeraden gefitted werden,
• – einer Berechnungseinheit 68, in der aus den Regressionsgeraden die Messparameter bestimmt werden.

A signal processing unit 51 . 52 the evaluation unit 5 exists, as in 11 is shown, essentially from the following functional units:

• - An analog-to-digital converter 59 .
• - a downstream bandpass 60 , being that of the photodetectors 21a . 21b ; 21c . 21d forwarded signals first after passing through the analog-to-digital converter 59 with the bandpass 60 be filtered to remove the DC and high frequency noise,
• - a Hilbert transformation unit 63 in which the signal envelopes are determined,
• - An amplitude normalization unit 65 in which the signals are normalized,
• - A Gaußfitting unit 64 in which the envelopes are fitted with Gaussian functions to thereby determine the start and end times (defined via the 1 / e ² threshold) as well as the time of the maximum amplitude t _Max , where the start and end times define a time window,
• - One of the amplitude normalization unit 65 downstream FFT unit 66 in which the time window is used for the short-time fast Fourier transformation (FFT), whereby the short-term FFT, which pushes an evaluation window over the time signals, is used to calculate the period duration-time functions,
• - a regression unit 67 in which regression lines are added to the period duration-time functions,
• - a calculation unit 68 in which the measurement parameters are determined from the regression line.

On the output side, the evaluation unit 5 a functional unit 57 for the coordinate transformation of the calculated velocity components at the passage X ₀ , Y ₀ , wherein the functional unit 57 with a display and / or output unit 58 in which is optionally the trajectory angle to the Z axis as a direction indication of the trajectory of the particles 23 are specifiable.

The functional unit 57 for coordinate transformation, in which an averaging of the two lateral velocity component v _z takes place, is designed such that it determines the passage location X ₀ , Y ₀ and the velocity components via the passage location X ₀ , Y ₀ and the local local strip spacings d ₁ , d ₂ for the first transmission optics 91 and the local stripe spacings d ₃ , d ₄ for the second transmission optics 92 calculated.

The device according to the invention 1 determined according to 1 the areal and three-component speed profile. It is in 1 The XYZ coordinate system shown is a coordinate system rotated with respect to the prior art xyz coordinate system, with the z-axis and the xy plane respectively rotated to the Z-axis and the XY-plane.

As the device 1 according to 1 from two orthogonally arranged transmission optics 91 . 92 which are also based on the principle of laser Doppler anemometry (LDA), are used in any transmission optics 91 . 92 two superimposed, fan-shaped interference fringe systems 61 . 62 , which must be physically distinguishable, used. From the scattered light of a particle carried by a flow 23 can be the respective lateral and the axial velocity component and the axial position of the particle 23 in the measuring volume 6 . 7 determine. By combining the two transmission optics 91 . 92 with mutually orthogonal axes 22 . 25 Both the two-dimensional X, Y position in the spanned XY plane and all three velocity components v _X , v _Y , v _Z for a single particle 23 determine. By measuring many particles Σ23, a two-dimensional, areal and three-component image of the flow velocity is obtained as a velocity profile.

That's why the measurement volume 6 . 7 superimposed. The optical axes 22 . 25 the two transmission optics 91 . 92 are orthogonal to each other. In 1 are the arrangement of the transmission optics 91 . 92 and the default XYZ coordinate system. The receiving optics 4 can be placed anywhere in the room and consists of the same as in 2 shown line sensor 2 only from a convex lens 17 that the stray light 26 into the multimode fiber 20 coupled and the photodetectors 21a . 21b feeds.

The following Table 1 shows how the individual sizes of the two transmission optics 91 . 92 are obtained, the axis designations according to 1 to be understood. As to every transmission optics 91 . 92 only one location coordinate Y or X is measured and both optical axes 22 . 25 are arranged orthogonal to each other, a two-dimensional coordinate of the location X ₀ , Y _{0 is obtained} at t = 0. The measuring range is through the cutting measuring range 8th the individual measurement volume 6 . 7 given. The same applies to the velocity components:
With every transmission optics 91 . 92 Two speed components are detected. The orthogonal arrangement consequently detects all three velocity components v _X , v _Y , v _Z , with redundancy for the Z direction. The redundancy can be used to reduce the measurement uncertainty by averaging.

Table 1

In summary, it can be stated that the velocity vector with the three components v _X , v _Y , v _Z can be detected in a two-dimensional XY measurement range:

For the device 1 Thus, four measurement channels for four interference fringe systems, each with two per transmission optics 91 . 92 , as in 9 . 10 shown is needed. The evaluation of the burst signal pairs and the determination of the velocity profile takes place in the in 10 shown evaluation 5 ,

The evaluation unit 5 contains two signal processing units 51 . 52 for the two transmission optics 91 . 92 , where in 11 the signal processing unit 51 for the transmission optics 91 , also representative of the transmission optics 92 , is shown. Each signal processing unit 51 or 52 consists of several functional units, in each of which in 10 . 11 in a circuit block diagram specified course of detection of the time dependence of the Doppler frequency and the evaluation, which is preferably implemented with program technical means, eg in the graphical programming language LabVIEW done. Each signal processing unit 51 . 52 has two input channels on the input side 53 . 54 respectively. 55 . 56 using the photodetectors 21a . 21b such as 21c . 21d the demultiplexing unit 32 communicate as in 9 is shown. On the output side, the evaluation unit 5 a functional unit 57 for the coordinate transformation of the calculated velocity components at the passage X ₀ , Y ₀ , wherein the functional unit 57 with a display and / or output unit 58 communicates. Likewise, the trajectory angles to the Z-axis can be given as a direction indication of the particle trajectory.

The following is the in 11 illustrated signal processing unit 51 , also representative of the analogue signal processing unit 52 explained in more detail with their functioning.

In the signal processing unit 51 are the two input channels 53 . 54 present to which the two photodetectors 21a . 21b assigned. The of the photodetectors 21a . 21b Forwarded signals are first passed through an analog-to-digital converter 59 with a bandpass 60 filtered to remove the DC component and high-frequency noise. After that, using a Hilbert transform unit 63 the signal envelope determines and the signals in an amplitude normalization unit 65 normalized. The envelopes are in a Gauss fitting unit 64 fitted with Gaussian functions to thereby determine the start and end times (defined by the 1 / e ² threshold) and the time of the maximum amplitude t _Max . The start and end times define a time window which is in one of the amplitude normalization unit 65 downstream FFT unit 66 is used for the short-term fast Fourier transform (FFT). The time of the maximum amplitude t _Max defines the passage through the optical axes 22 , wherein with the current Doppler frequencies f ₁ , f ₂ at the time t _max, the output position Y _{0 is} calculated later. To calculate the period duration-time functions, the short-time FFT is used, which shifts an evaluation window over the time signals. The period duration time functions are stored in the regression unit 67 Regression lines are fitted out of which in a calculation unit 68 the actual measurement parameters are determined:
The instantaneous Doppler frequencies f ₁ , f ₂ at the time t _Max are used to transmit via the calibration radio tion in equation (I), as in 6 shown, the passage position Y ₀ through the intersection of the optical axis 22 to investigate. With the local strip distances d ₁ (Y ₀ ), d ₂ (Y ₀ ) at the passage position Y ₀ , the lateral velocity component v _{z is} calculated using equation (II). Finally, the axial velocity component v _{Y is} determined by means of the equation (XI) via the slopes of the regression line of the period duration-time function T (t). Thus, all web sizes of the trajectory 27 of the particle 23 certainly. From the equation (V), the respective angle α of the normal (Z axis) to the optical axis can additionally be determined 22 be calculated.

As for the second transmission optics 92 the same results with the signal processing unit 52 with respect to the passage position X ₀ , the lateral velocity component v _z and the axial velocity component v _X are obtained, in the functional unit 57 for the coordinate transformation, in which an averaging of the two Lateralge speed component v _Z can take place, the passage X ₀ , Y ₀ obtained. In principle, be it the velocity components v _x, v _y, v _Z via the Durchtrittsort X _0, Y ₀ and the local local strip distances d _1, d ₂ for the first transmission optics 91 and the local stripe spacings d ₃ , d ₄ for the second transmission optics 92 calculated.

The specified method for determining the velocity profile in the area of the evaluation unit 5 , in which the time-resolved frequency measurement is shown, the wavelet transformation can also be carried out with other transformations, eg the Wigner-Ville transformation.

Essential is it that all interference fringe systems are designed to do this be that they are physically distinguishable. In addition to the previous one also presented wavelength division multiplexing techniques other multiplexing techniques such as frequency and time division multiplexing or be used in combination of these, etc.

With regard to the distinguishability of the four interference fringes by multiplexing, as in the 9 . 10 shown, four measuring channels for the two transmission optics 91 . 92 , All multiplexing techniques and these can be combined with each other.

In Table 2 is an overview of the required Components shown when different combinations of wavelength and Frequency division multiplexing can be used.

Table 2:

When using four different wavelengths λ ₁ , λ ₂ , λ ₃ , λ ₄ - pure wavelength division multiplexing - the results 9 , For each of the multiplexing methods mentioned in Table 2, four input channels to the evaluation unit are always formed for the signal forwarding from the demultiplexing unit.

In the embodiment, the device 1 to an arrangement of the two transmission optics 91 . 92 based, their optical axes 22 . 25 are arranged orthogonal to each other. The device works similarly when the optical axes are inclined at an angle of 80 ° or an angle below or are arranged obliquely to each other. Then an additional corresponding coordinate transformation is provided.

Above all, the method according to the invention enables a high degree of precision training, the measurement uncertainty of the position determination being in the micrometer range and the relative measurement uncertainty of the speed being less than 5 · 10 ^-9 .

Remarkable is also that in the process of reconstruction of the velocity profile no camera, but a simply trained receiving optics, the with big Working distance can be placed anywhere in the room used can be.

The inventive device can be referred to as a 2D3C sensor or as a field sensor, because with the device a planar and three-component measurement of the velocity for determination a velocity profile of arbitrarily directed flows are performed can.

1

contraption

2

line sensor

31

First demultiplexing

32

second demultiplexing

4

receiving optics

5

evaluation

6

first measuring volume

7

second measuring volume

8th

Cut range

9

transmission optics

10a

first laser diode with wavelength λ ₁

10b

second laser diode with wavelength λ ₂

11a

first collimator lens

11b

second collimator lens

12

dichroic mirror

13

focusing lens

14

Transmission diffraction grating

15a

first achromatic lens

15b

second achromatic lens

16

cover

17

convex lens

18

second dichroic mirror

19

collimator lens

20

Multimode fiber

21a

first photodetector

21b

second photodetector

21c

third photodetector

21d

fourth photodetector

22

optical axis

23

particle

24

Plate boundary layer

25

optical Axis of the second transmission optics

26

scattered light

27

trajectory of a particle

28a

first scattered light component with wavelength λ ₁

28b

second scattered light component with wavelength λ ₂

51

first Signal processing unit

52

second Signal processing unit

53

first channel

54

second channel

55

third channel

56

fourth channel

57

functional unit for coordinate transformation

58

Display- and / or output unit

59

Analog to digital converter

60

bandpass

61

first fan-shaped interference fringe system

62

second fan-shaped interference fringe system

63

Hilbert transform unit

64

Gaußfitting unit

65

Amplitude normalization unit

66

FFT unit

67

Regression unit

68

calculation unit

z ₀

Passage position for one line sensor

X ₀ , Y ₀

Durchtrittsort

α

angle the flow direction the particles to

normal the transmission optical axis

λ ₁

first wavelength

λ ₂

second wavelength

λ ₃

third wavelength

λ ₄

fourth wavelength

f ₁ (t)

first Doppler frequency

f ₂ (t)

second Doppler frequency

f ₃ (t)

third Doppler frequency

f ₄ (t)

fourth Doppler frequency

q (z)

calibration function

d ₁ (z)

first fringe spacing

d ₂ (z)

second fringe spacing

d ₃ (z)

second fringe spacing

d ₄ (z)

second fringe spacing

v _X

first Lateralgeschwindigkeitskomponente

v _Y

second Lateralgeschwindigkeitskomponente

v _Z

axial velocity

r (t)

trajectory of the particle xyz coordinate system of a line sensor XYZ coordinate system the device

Claims (21)

Apparatus for the determination of velocity profiles of randomly directed flows according to the principle of laser Doppler anemometry with two superimposed fan-shaped interference fringes, which are physically distinguishable, wherein a transmitting optics linearly spaced on its optical axis is assigned a measuring volume consisting of two superimposed interference fringe systems in which an axis position and a position-related lateral velocity component of the particle can be determined via a receiving optical system and a downstream demultiplexing unit from the scattered light of the particles by means of an evaluation unit for signal processing of burst signal pairs, characterized in that - two transmitting optics ( 91 . 92 ) are provided, which with respect to their optical axes ( 22 . 25 ) are arranged inclined to each other, wherein the two measuring volumes ( 6 . 7 ) to a cutting range ( 8th ) are superimposed in a given XYZ coordinate system, - the receiving optics ( 4 ) in the space around the cutting measuring range ( 8th ) is arranged, which the the transmission optics ( 91 . 92 ) associated demultiplexing unit ( 32 ), and - wherein the evaluation unit ( 5 ) with two of the demultiplexing unit ( 32 ) downstream signal processing units ( 51 . 52 ) is formed such that both a two-dimensional XY location (X ₀ , Y ₀ ) in the in the section measuring range ( 8th ) and all three velocity components v _X , v _Y , v _Z for the particles ( 23 ) can be determined to associated velocity profiles. Apparatus according to claim 1, characterized in that the two transmitting optics ( 91 . 92 ) with respect to their optical axes ( 22 . 25 ) are arranged orthogonal to each other. Apparatus according to claim 1 and / or 2, characterized in that in oblique particle trajectories, ie with non-vanishing axial velocity components v _X , v _Y, the burst signal pairs have a frequency change with time, the period duration change with time directly proportional to the Axialgeschwindigkeitskomponenten v _X , v _Y is and for a single particle ( 23 ) - the lateral velocity component v _{Z of} the velocity v, - the axial velocity components v _X , v _{Y of} the velocity v and The passage X ₀ , Y _{0 of} the particle ( 23 ) through the optical axes ( 22 . 25 ), wherein the determination of the axial velocity components v _X , v _{Y is} directionally internal. Device according to any preceding claim, characterized in that the transmitting optics ( 91 . 92 ) - two laser diodes ( 10a . 10b ) of different wavelengths λ ₁ ≠ λ ₂ , λ ₃ ≠ λ ₄ - each one convex lens ( 11a . 11b ), - a dichroic mirror ( 12 ), - a convex lens ( 13 ), - a transmission diffraction grating ( 14 ), - two achromatic lenses ( 15a . 15b ), which form in their arrangement a Kepler telescope, - optional aperture ( 16 ), which is only the +1. and -1. Pass diffraction orders and block all other diffraction orders contains. Apparatus according to claim 1, characterized in that the receiving optics ( 4 ) a convex lens system ( 17 ) from which optionally a multimode fiber ( 29 ) to the demultiplexing unit ( 32 ) is guided. Apparatus according to claim 5, characterized in that - the receiving optics ( 4 ) for the two transmission optics ( 91 . 92 ) a demultiplexing unit ( 32 ), which has the following components: optionally an input for the multimode fiber ( 20 ), - an input-side collimator lens ( 19 ), - three dichroic mirrors ( 18 ), - four output-side collimating lenses ( 19 ) and - four photodetectors ( 21a . 21b . 21c . 21d ) for signal forwarding to the evaluation unit ( 5 ). Apparatus according to claim 4 to 6, characterized in that four input channels ( 53 . 54 . 55 . 56 ) for four interference fringe systems, each with two per emitting optics ( 91 . 92 ) are provided. Apparatus according to claim 1, characterized in that the evaluation unit ( 5 ) two signal processing units ( 51 . 52 ) for the two transmission optics ( 91 . 92 ), each signal processing unit ( 51 . 52 ) consists of several functional units, in which the specified course of the detection of the time dependence of the Doppler frequency and the evaluation, which is preferably realized with programmatic means, for example in the graphical programming language LabVIEW, takes place. Apparatus according to claim 8, characterized in that each signal processing unit ( 51 . 52 ) input side two input channels ( 53 . 54 ; 55 . 56 ), which with the photodetectors ( 21a . 21b ; 21c . 21d ) of the demultiplexing unit ( 32 ) keep in touch. Apparatus according to claim 9, characterized in that a signal processing unit ( 51 . 52 ) of the evaluation unit ( 5 ) consists essentially of the following functional units: - an analog-to-digital converter ( 59 ), - a downstream bandpass ( 60 ), whereas those of the photodetectors ( 21a . 21b ; 21c . 21d ) forwarded signals after passage through the analog-to-digital converter ( 59 ) with the bandpass ( 60 ) are filtered to remove the DC and high frequency noise, a Hilbert transform unit ( 63 ), in which the signal envelopes are determined, - an amplitude normalization unit ( 65 ), in which the signals are normalized, - a Gauss fitting unit ( 64 ) in which the envelopes are fitted with Gaussian functions to thereby determine the start and end times (defined over the 1 / e ² threshold) and the time of the maximum amplitude t _Max , the start and end times defining a time window, One of the amplitude normalization unit ( 65 ) downstream FFT unit ( 66 ), in which the time window for the short-time fast Fourier transform (FFT) is used, wherein for calculating the period duration-time functions, the short-term FFT is used, which pushes an evaluation window on the time signals, - a regression unit ( 67 ) in which regression lines are added to the period duration-time functions - a calculation unit ( 68 ), in which the measurement parameters are determined from the regression line. Apparatus according to claim 10, characterized in that on the output side, the evaluation unit ( 5 ) a functional unit ( 57 ) for coordinate transformation of the calculated velocity components at the transit location X ₀ , Y ₀ , wherein the functional unit ( 57 ) with a display and / or output unit ( 58 ) in which either the trajectory angle to the Z axis as a direction indication of the trajectory of the particles ( 23 ) are specifiable. Apparatus according to claim 11, characterized in that the functional unit ( 57 ) for coordinate transformation, in which an averaging of the two lateral velocity component v _Z takes place, is designed such that it determines the passage location X ₀ , Y ₀ and the velocity components via the passage location X ₀ , Y ₀ and the local strip spacings d ₁ , d ₂ for the first transmission optics ( 91 ) and the local stripe spacings d ₃ , d ₄ for the second transmission optics ( 92 ). Method for the determination of velocity profiles of particles in randomly directed flows according to the principle of laser Doppler anemometry with two superimposed fan-shaped interference fringes that are physically distinguishable, wherein the transmitting optics are linearly spaced on their optical axis associated with the interference fringe systems associated measurement volume, in an axis position and a position-related lateral velocity component of the particle are determined via a receiving optical system and a downstream demultiplexing unit from the scattered light of the particles by means of an evaluation unit, characterized by the following steps: - superposition of two mutually inclined, two fan-shaped interference fringe systems of two transmitting optics ( 91 . 92 ), whereby the fan-shaped interference fringe systems are physically distinguishable by multiplexing methods and the optical axes ( 22 . 25 ) are arranged inclined to each other, - evaluation of the Doppler frequencies f ₁ , f ₂ obtained from both inclined to each other, fan-shaped interference fringe systems; f ₃ , f ₄ for a one-dimensional position determination of the particle ( 23 ) within a measuring volume ( 6 ; 7 ) of two fan-shaped interference fringe systems, - combined evaluation of the burst signal pairs obtained from the two different mutually inclined interference fringe systems for a two-dimensional position determination X, Y in a slice measuring range ( 8th ) of the measuring volume ( 6 . 7 ) of the two different mutually inclined interference fringe systems by means of the evaluation unit ( 5 ) and frequency-time analysis of the burst signal pairs obtained from the mutually inclined interference fringe systems for determining the two axial velocity components v _X , v _Y in the evaluation unit lying in the XY plane spanned by the two interference fringe systems ( 5 ). A method according to claim 13, characterized in that in orthogonal arrangement of the two interference fringe systems lying in the XY plane speed components v _X , v _{Y are determined} without additional transformation calculations. Method according to claim 13 and / or 14, characterized in that by means of a transmission optics ( 91 . 92 ) - two superimposed fan-shaped interference fringes are formed such that by evaluating the Doppler frequencies f ₁ , f ₂ ; obtained from both interference fringe systems; f ₃ , f ₄ a position determination within the interference fringe system for a position determination X, Y of the particles ( 23 ) is performed by a frequency-time analysis of the burst signal pairs obtained in the interference fringe systems in the evaluation unit ( 5 ) a determination of the respectively associated lateral velocity component v _Z and - a direction-sensitive measurement of the axial velocity components v _X , v _{Y are} performed. Method according to the preceding claims 13 to 15, characterized in that the Axialgeschwindigkeitskomponenten v _X , v _Y directly over the temporal change of the period duration time function T (t) are determined, wherein the time dependence of the Doppler frequency f ₁ , f ₂ ; f ₃ , f _{4 is} a measure of the ratio between in each case one axial velocity component v _X , v _Y and the lateral velocity component v _Z , the ratio being represented by the respective angle α as an expression of the oblique trajectory of the particle (FIG. 23 ) is given. Method according to any of the preceding claims 13 to 16, characterized in that the Doppler frequency f ₁ , f ₂ , f ₃ , f ₄ can both rise and fall, so that a difference between a positive and a negative speed component is un and the axial velocity components v _X , v _{Y is} thus determined to be directionally aware. Process according to any one of Claims 13 to 17, characterized in that a sufficiently large number of particles ( 23 ) is evaluated in order to determine the 8th ) to determine prevailing velocity profile. A method according to claim 13 to 18, characterized in that the determination of the velocity profile in the region of the evaluation unit ( 5 ) with other transformations, eg the Wigner-Ville transformation, the wavelet transformation is performed. Method according to claims 13 to 19, characterized that in addition to the method of wavelength division multiplexing other Multiplexing such as frequency and time division multiplexing or in combination of these are used. Method according to claim 13 to 20, characterized that it by means of the device according to at least one of claims 1 to 12 performed becomes.