A method for the quantitative acquisition of flow patterns in fluid flows in which a medium (e.g., a gas or a liquid) and the particles contained therein and carried in the flow are set in motion in a transparent flow object. The method provides that a flow object is transilluminated by a laser light fanned out on a plane parallel to the longitudinal axis of the flow object. A scattering of the laser light by the particles is detected by a camera positioned at a right angle to the longitudinal channel axis and moving in the vertical and horizontal directions, and can be analyzed with an analysis unit connected downstream from the camera. The analysis unit is calibrated by quantitatively comparing an image, which has an object-to-image ratio and which is recorded inside the flow object by the camera, to an image having an object-to-image ratio and recorded outside the flow object.

A digital particle image velovimetry (DPIV) method for contactless measurement of three dimensional flow velocities comprising the steps of seeding a flow with tracer particles; repeatedly illuminating a plane-like interrogation volume of the seeded flow; projecting the repeatedly illuminated interrogation volume onto at least a photo sensor in a projection direction for recording pictures of the illuminated interrogation volume; and determining the three dimensional flow velocities from the pictures of the repeatedly illuminated interrogation volume recorded by the photo sensor. The plane-like interrogation volume of the invention comprises at least two partial volumes positioned parallelly parallel to each other with regard to the projection direction. The step of repeatedly illuminating the interrogation volume comprises the step of illuminating the partial volumes in such a way that the pictures of different partial volumes are distinguishable from each other. The step of determing the three dimensional flow velocities of the flow comprises the steps of calculating a local autocorrelation function of a double exposed picture of the same partial volume, or calculating a local cross-correlation function between two separate pictures of the same partial volume, calculating a local cross-correlation function between two pictures of two different partial volumes, determining the sign of the out-of-plane component of the local flow velocities by using the location of a peak of the local cross-correlation function between the two pictures of the two different partial volumes, and determining the magnitude of the out-of-plane component of the local flow velocities by using the peak heights of peaks of both local correlation functions.

A process and apparatus are disclosed for generating object traces representing the movement of objects through a measuring space. The measuring space can be illuminated by a laser or other light source, or alternatively the objects can be self-illuminating. In either event, light from the objects is detected over a finite acquisition time, to generate the object traces. During a predetermined portion of the acquisition time, preferably near the end, one of several parameters that govern the object trace width is altered to increase the width, thereby giving the object trace the form of an arrow or vector. The altered parameter can be the brightness of illumination, the sensitivity of the image detector, or the position or state of system components, in particular the image detector, a lens or other active optical component between the objects and the detector, or an optical component between the light source and the objects.

A method of multi-resolution adaptive correlation processing of images, such as seeded fluid flow images, to efficiently increase the spatial resolution and dynamic range of detecting particle image displacements in the images. The technique takes full advantage of the multi-resolution characteristic of the discrete correlation function by starting the processing at the smallest scale and if necessary gradually building correlation planes into larger interrogation areas based on the result of inter-level correlation correction and validation. It is shown that the method can be implemented in both direct and FFT based correlation algorithms with greatly reduced computational complexity. Processing the images at the lowest scale (e.g. pixel or particle image size) allows the combination of correlation planes of various shapes both in space and in time for maximizing the correlation plane signal-to-noise ratio or for estimating statistical flow parameters.

This invention is a one-dimensional elementary motion detector that measu the linear optical flow in a small subsection of the visual field. This sensor measures motion by tracking the movement of a feature across the visual field and measuring the time required to move from one location to the next. First a one-dimensional image is sampled from the visual field using a linear photoreceptor array. Feature detectors, such as edge detectors, are created with simple circuitry that performs simple computations on photoreceptor outputs. The detection of the feature's location is performed using a winner-take-all (WTA) mechanism on feature detector outputs. Motion detection is the performed by monitoring the location of the high WTA output in time to detect transitions corresponding to motion. The correspondence problem is solved by ignoring transitions to and from the end lines of the WTA output bus. Speed measurement is performed by measuring the time between WTA output transitions. This invention operates in a one-dimensional subspace of the two-dimensional visual field. The conversion of a two-dimensional image section to a one-dimensional image is performed by a specially shaped photoreceptor array which preserves image information in one direction but filters out image information in the perpendicular direction. Thus this sensor measures the projection of the 2-D optical flow vector onto the vector representing the sensor's orientation. By placing several of these sensors in different orientations and using vector arithmetic, the 2-D optical flow vector can be determined.