Optics: measuring and testing – Velocity or velocity/height measuring – With light detector
Patent
1996-03-25
1998-09-22
Hellner, Mark
Optics: measuring and testing
Velocity or velocity/height measuring
With light detector
7386106, G01P 336, G01P 1712
Patent
active
058122486
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention concerns a process for the determination of the direction of recorded traces of moved objects immediately upon acquisition by an image detector. The detected object traces upon acquisition provide graphical information in arrow or vector form. The objects can be illuminated or self-illuminating bodies of various sizes. Small illuminated particles such as molecules or particles transported together in a flow, and larger illuminated moved objects can reproduce traces on an image detector. It is therefore a presupposition of the process that the objects produce traces on the detector element during the exposure or integration time of the image detector. It is characteristic of the process that the detected object traces are provided upon acquisition with graphical information in arrow or vector form, either through the changing of the light output irradiating the image detector or through the changing of the sensitivity of the image detector.
Similar processes and devices, without the graphical direction identification of the invention, are used in flow and particle measurement technology. Such technology involves inferring from detected particle traces the velocity field of a flow or a particle phase in an illuminated measurement space. The objects or particles employed as tracers are in many cases so small that they can follow the current with sufficient precision. In general, they are illuminated by a laser light source, whose light beam is transformed into a light sectional plane. The acquisition of the particle traces during an exposure or integration time adapted to the velocity of the particle movement leads to particle traces on the image detector (e.g. film, semiconductor image sensor). The traces permit the velocity field of the current to be seen. This sort of trace acquisition based on illuminated or self-illuminating particles is also found in other ranges of object size, for example in process engineering involving following larger particles, or in physics, where traces of particles and nuclear components are made visible, or in medical technology, e.g. following the movement of blood corpuscles.
A rough classification of existing particle movement measuring follows from whether measurement is taken at a fixed point in the measurement space over a period of time, or whether an extended region of the measurement space is surveyed at a fixed point in time. Point measurement processes provide for the most part time-averaged information, and whole field measurement processes ("Whole Field Techniques") provide predominantly momentary movement information. The present invention belongs in the sphere of the whole field measurement processes, in which object traces in an entire image field (a section of a measurement space) are recorded and analyzed at a fixed point in time. Hitherto, particle tracing anemometry, also called "particle tracing anemometry" (PTA), was applied to such measurement tasks, as well as laser speckle velocimetry, also called particle image velocimetry (PIV). With PTA, the entire image-producing trace of a particle is recorded, while with PIV, through the pulse activity of the illumination source, only the starting and ending points of the particle trace are recorded. In these processes, as well as holographic recording processes, object traces are certainly very easily recorded, but only with respect to the magnitude of the velocity. Without additional aids, the direction of the movement cannot be inferred from the recorded particle or object trace.
For this reason, experimenters in particle tracing anemometry have developed encoding processes that allow identification of the direction of an object trace. For example, through the interruption of the illumination, a sort of pulse-encoding of the object trace is obtained that distinguishes the direction of the movement. See Khaligi, B., Yong H. Lee, 1989: "Particle Tracking Velocimetry: An Automatic Image Processing Algorithm", Applied Optics, Vol. 28, No. 20, pp. 4328-4332. A whole-field
REFERENCES:
patent: 4866639 (1989-09-01), Adrian
patent: 4988191 (1991-01-01), Adrian et al.
patent: 5153665 (1992-10-01), Weinstein
patent: 5491642 (1996-02-01), Wormell et al.
Kaiser Andreas
Ruck Bodo
Hellner Mark
Niebuhr Frederick W.
TSI Corporation
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