A method is provided for detecting primary gas flows (18) in flow chambers (10). The primary gas (18) flowing in a flow chamber (10) is locally seeded with a seed substance and the movement of the seed substance, representative of the flow of the primary gas (18), is detected by imaging by an image detector (28) and an imaging optics (30) arranged in front of said image detector (28). A gas mixture (34) that moves along with the primary gas (18) without relative motion and that has a refractive index distinguishable from that of the primary gas (18) is used as the seed substance, and imaging detection is carried out by a background schlieren measurement method.
A method calibrates an optical measurement set-up with a measurement volume seeded with particles and at least two cameras so that the measurement volume can be mapped from different observation angles. The method includes simultaneously mapping the measurement volume by the cameras to produce images; rectifying each camera image in relation to a common reference plane in the measurement volume by using the respective pre-calibrated mapping function; performing two-dimensional correlation for at least one pair of rectified camera images to produce correlation fields that present an elongate correlation maxima band for each correlation field; reducing the correlation maxima band to a straight line representing the band; determining the distance of this representative straight line from the coordinate origin of the correlation field as a correction value, using the determined correction values to correct the mapping functions of those cameras for which rectified camera images were included in the correlations.
G06T 7/80 - Analyse des images capturées pour déterminer les paramètres de caméra intrinsèques ou extrinsèques, c. à d. étalonnage de caméra
G06T 7/32 - Détermination des paramètres de transformation pour l'alignement des images, c. à d. recalage des images utilisant des procédés basés sur la corrélation
G01P 5/20 - Mesure de la vitesse des fluides, p.ex. d'un courant atmosphérique; Mesure de la vitesse de corps, p.ex. navires, aéronefs, par rapport à des fluides en mesurant le temps mis par le fluide à parcourir une distance déterminée en utilisant des particules entraînées par un courant de fluide
3.
Method of tracking a plurality of point-shaped objects in a three-dimensional space
For tracking a plurality of objects in a three-dimensional space two-dimensional pictures objects are recorded with two black and white cameras out of two different imaging directions. Both first pictures and second pictures of the two cameras are simultaneously exposed at two points in time in equal ways, a point in time at which the second pictures are exposed for a first time following to a point in time at which the first pictures are exposed for a last time at a much shorter interval than the two points in time of exposure of both the first and second pictures. First and second distributions of real positions of the individual objects are determined from their images in the first and second pictures, respectively; and temporally resolved trajectories of the individual objects in the three-dimensional space are determined from the first and second distributions of real positions.
G01N 15/14 - Recherche par des moyens électro-optiques
G01P 5/00 - Mesure de la vitesse des fluides, p.ex. d'un courant atmosphérique; Mesure de la vitesse de corps, p.ex. navires, aéronefs, par rapport à des fluides
G01P 5/20 - Mesure de la vitesse des fluides, p.ex. d'un courant atmosphérique; Mesure de la vitesse de corps, p.ex. navires, aéronefs, par rapport à des fluides en mesurant le temps mis par le fluide à parcourir une distance déterminée en utilisant des particules entraînées par un courant de fluide
G01B 11/00 - Dispositions pour la mesure caractérisées par l'utilisation de techniques optiques
G06K 9/62 - Méthodes ou dispositions pour la reconnaissance utilisant des moyens électroniques
G06T 7/70 - Détermination de la position ou de l'orientation des objets ou des caméras
G01N 21/17 - Systèmes dans lesquels la lumière incidente est modifiée suivant les propriétés du matériau examiné
For determining a changing spatial distribution of particles at each of multiple points in time, real two-dimensional images of the particles are recorded with different mapping functions. An estimated spatial distribution of the particles is provided. Virtual two-dimensional images of the estimated spatial distribution are calculated applying the different mapping functions. Differences between the virtual and the real two-dimensional images are determined; and the estimated spatial distribution of the particles are varied for reducing the differences to obtain a spatial distribution approximated to the actual spatial distribution of the particles. The estimated spatial distribution of the particles is provided in that the locations of the individual particles in a spatial distribution approximated for one other point in time are shifted dependently on how the locations of the individual particles have changed between at least two spatial distributions approximated for at least two other points in time.
G06K 9/00 - Méthodes ou dispositions pour la lecture ou la reconnaissance de caractères imprimés ou écrits ou pour la reconnaissance de formes, p.ex. d'empreintes digitales
G01P 5/20 - Mesure de la vitesse des fluides, p.ex. d'un courant atmosphérique; Mesure de la vitesse de corps, p.ex. navires, aéronefs, par rapport à des fluides en mesurant le temps mis par le fluide à parcourir une distance déterminée en utilisant des particules entraînées par un courant de fluide
G01P 5/00 - Mesure de la vitesse des fluides, p.ex. d'un courant atmosphérique; Mesure de la vitesse de corps, p.ex. navires, aéronefs, par rapport à des fluides
G06T 7/246 - Analyse du mouvement utilisant des procédés basés sur les caractéristiques, p.ex. le suivi des coins ou des segments
5.
Method for determining a set of optical imaging functions for three-dimensional flow measurement
The invention relates to a method for determining a set of optical imaging functions that describe the imaging of a measuring volume onto each of a plurality of detector surfaces on which the measuring volume can be imaged at in each case a different observation angle by means of detection optics. In addition to the assignment of in each case one image position (x, y) to each volume position (X, Y, Z), the method according to the invention envisages that the shape of the image of a punctiform particle in the measuring volume be described by shape parameter values (a, b, 100 , I) and that the corresponding set of shape parameter values be assigned to each volume position (X, Y. Z) for each detector surface.
G01P 5/00 - Mesure de la vitesse des fluides, p.ex. d'un courant atmosphérique; Mesure de la vitesse de corps, p.ex. navires, aéronefs, par rapport à des fluides
6.
Method for the contact-free measurement of deformations of a surface of a measured object
The invention relates to a method for the contact-free measurement of deformations of a surface of a object in which a series of individual images is captured in each of two time windows (T1, T2), wherein between every two individual image captures the image detector is displaced relative to the object and parallel to its detector surface by an optical offset of the size of a fraction of a pixel up to a few pixels, the individual images of the first time window (T1) are processed in pairs with the individual images of the second time window (T2) to produce a set of individual deformation fields (18) and an average of the individual deformation fields (18) is calculated as an output deformation field (20).
G06K 9/00 - Méthodes ou dispositions pour la lecture ou la reconnaissance de caractères imprimés ou écrits ou pour la reconnaissance de formes, p.ex. d'empreintes digitales
G01B 11/16 - Dispositions pour la mesure caractérisées par l'utilisation de techniques optiques pour mesurer la déformation dans un solide, p.ex. indicateur optique de déformation
7.
Method of determining a three-dimensional velocity field in a volume
A method of determining a three-dimensional velocity field in a volume having particles, the particles within the volume being excited to radiate by illuminating the volume, including two or more cameras simultaneously capturing images of the observation volume at two different instants of time, the observation volume being divided into small volume elements (voxels), each voxel being projected onto image points of the cameras, the intensity of all the voxels being reconstructed from the measured intensity of the respective associated image points, a plurality of voxels being combined to form an interrogation volume, and a displacement vector being determined by a three-dimensional cross correlation of the two interrogation volumes.
G06K 9/00 - Méthodes ou dispositions pour la lecture ou la reconnaissance de caractères imprimés ou écrits ou pour la reconnaissance de formes, p.ex. d'empreintes digitales
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