Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: An inherent pattern image (100, 100F) of a test object (10) is recorded when the test object is illuminated with uniform illumination light, and a projection pattern image (200, 200F) is recorded when the test object is illuminated with a spatially modulated projection pattern. A planar displacement vector field (110, 110F) is calculated from the inherent pattern image, and a shape (210, 210F) is calculated from the projection pattern image. An image of the first type is recorded at time (tT), and images of the second type are recorded at times (tT?; tT+) before and after the time (tT). A representation of the test object at the test time (tT) is estimated by averaging. A spatial displacement vector field (300) is based on the calculated representation of the test object of the first image type and the representation of the test object estimated from the images of the second type.

Abstract: 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.

Abstract: 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).

Abstract: An inherent pattern image (100, 100F) of a test object (10) is recorded when the test object is illuminated with uniform illumination light, and a projection pattern image (200, 200F) is recorded when the test object is illuminated with a spatially modulated projection pattern. A planar displacement vector field (110, 110F) is calculated from the inherent pattern image, and a shape (210, 210F) is calculated from the projection pattern image. An image of the first type is recorded at time (tT), and images of the second type are recorded at times (tT?; tT+) before and after the time (tT). A representation of the test object at the test time (tT) is estimated by averaging. A spatial displacement vector field (300) is based on the calculated representation of the test object of the first image type and the representation of the test object estimated from the images of the second type.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: The subject matter of the invention is a method of correcting a volume imaging equation for more accurate determination of a velocity field of particles in a volume, said volume being captured from different directions by at least two cameras, a coarse calibration of the position of the cameras relative to each other and relative to the volume of concern being carried out first by determining an imaging equation that associates with the coordinates (X, Y, Z) of a point in the volume the corresponding camera picture coordinates xi, yi of each camera i, all the cameras then capturing simultaneously in the same unchanged position particles in a volume, the position (X, Y, Z) of a particle in the volume being approximated by means of a known triangulation method using the calculated position xi, yi of a particle in the camera pictures, this position (X, Y, Z) being imaged through the original imaging equation onto a position xi?, yi? in the camera images of the at least two cameras, a correction factor for the im

Abstract: The invention relates to a method for determining flow conditions in a measured volume permeated by a fluid spiked with optically detectable particles. A plurality of two-dimensional images of the particle distribution is thereby created at each of a plurality of times, an estimated particle distribution is determined therefrom, and a three-dimensional displacement vector field is calculated. According to the invention, a transfer function for the image detectors used is first determined, by means of which the real distribution is mapped by the image detector. Starting from a roughly estimated initial distribution, and by means of the transfer function, virtual images of the estimated distribution are then calculated and compared to the associated real images. The estimated distribution is modified in an iterative method until sufficient matching of the virtual and real images has been achieved.

Abstract: 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).

Abstract: 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.

Abstract: The subject matter of the invention is a method of correcting a volume imaging equation for more accurate determination of a velocity field of particles in a volume, said volume being captured from different directions by at least two cameras, a coarse calibration of the position of the cameras relative to each other and relative to the volume of concern being carried out first by determining an imaging equation that associates with the coordinates (X, Y, Z) of a point in the volume the corresponding camera picture coordinates xi, yi of each camera i, all the cameras then capturing simultaneously in the same unchanged position particles in a volume, the position (X, Y, Z) of a particle in the volume being approximated by means of a known triangulation method using the calculated position xi, yi of a particle in the camera pictures, this position (X, Y, Z) being imaged through the original imaging equation onto a position xi?, yi? in the camera images of the at least two cameras, a correction factor for the im

Abstract: A method of determining a three-dimensional velocity field in a volume, the particles within the volume being excited to radiate by illuminating said volume, a) at least two cameras simultaneously image capturing the observation volume at two different instants of time (t1, t2) at least, b) the observation volume being divided into small volume elements (voxels), c) each voxel being projected at the location x, y, z onto the image points (xn, yn) of the at least two cameras using a projection equation, d) the intensity of all the voxels being reconstructed from the measured intensity of the respective ones of the associated image points (xn, yn), e) a plurality of voxels being combined to form an interrogation volume, f) the displacement vector (dx, dy, dz) being determined at the times (t1, t2) at the same location by a three-dimensional cross correlation of the two interrogation volumes.

Abstract: The subject matter of the invention is a method for determining the imaging equation for self calibration with regard to performing stereo-PIV methods on visualized flows, said method being comprised of at least two cameras and one image sector, with the cameras viewing approximately the same area of the illuminated section but from different directions, the point correspondences between the two cameras being determined by measuring the displacement of the respective interrogation areas in the camera images using optical cross-correlation, the imaging equation being determined by means of approximation methods, using known internal and external camera parameters.