CZ2005672A3 - Device for determining position and/or size of at least one spherical body within a measured space of liquid - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for determining the position and / or size of at least one spherical body of a spherical shape in a measured fluid space (4) consisting of a photodetector and an optical system formed by a camera (3) with an objective (1), between the measured fluid space (4) and The photodetector is the focal length of two planes in a mutually perpendicular direction containing the optical axis.

Description

Apparatus for determining the position and / or size of at least one spherical body in a measured fluid space.

Technical field

The invention relates to a device for determining the position and / or size of at least one spherical body in a measured fluid space consisting of a photodetector and an optical system. Submitter ^ S) tt measurement method can be included in the field of technical optics - it uses contactless optical measurement.

BACKGROUND OF THE INVENTION

The current significant problem of industrial fluid technologies is the optimization of the presence of foreign phases, especially bubbles, in the process system. An example of this may be chemical reactors where an even distribution of bubbles throughout the reactor space is desired for an ideal course of chemical reactions. On the other hand, there are industrial technologies where the presence of a foreign phase in the medium is undesirable or or indicating a technological problem, such as in hydrodynamic machines or the glass industry. Therefore, the problem of detecting bubbles and determining their physical parameters has been the subject of much attention lately. Recent publications of methods and systems dealing with optical measurement of bubble dimensions using a camera using interference [1], Particle Image Velocimetry (PIV) methods [2], measuring the shape, velocity of bubbles, or even the distribution of bubbles in space optically using several independent cameras [3], [4], [5], [6]. For this purpose, the popular stereo PIV method has the disadvantages of having «6 (» t

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2use laser sweepers, two fast cameras and a complicated evaluation system, which makes the measurement very expensive. Therefore, the latest trend in this area is the search for new methods of measuring bubbles in space. Such new very sophisticated methods are for example the use of particle scattering of light [7] or the use of holographic methods [8], [9]. However, these methods require the use of a coherent laser-type source and are therefore again very expensive. Therefore, other measuring methods are still being developed, which would be sufficient with a single camera and simple lighting, where the spatial distribution of bubbles or objects is calculated, for example, from the temporal and optical parameters of a single camera image [10], [11] ]. The technically closest principle of measuring bubbles in space to the present measuring method is the method using a defocussed image of 3 apertures [13] and further developed to digital form [14]. However, this method works on a completely different principle and uses not only one photodeter, but a series of 3 photodetector elements to increase sensitivity, see US Patent 6,278,847.

[1] Y. Niwa, Y. Kamiya, T. Kawaguchi, M. Maeda, Bubble Sizing should Interferometric Laser Imaging, 10 ^th International Symposium on Applications of Laser Technique It Fluid Mechanics, Lisbon, Portugal 2000 [2] R. Lindken, W. Merzkirch, A novel PIV measurement technique for multi-phase flow and its application to two-phase bubbly flows. 4 ^th International Symposium on Particle Image Velocimeters Gottingen, Germany 2001 [3] I · Leifer, G. de Leeuw, LH Cohen, Optical Measurement of Bubbles: System Design and Application. Journal of Atmospheric and Ocean Technology, Vol. 1317-1332, 2003

-35 í i. Ter «« »i« «« lij! ttt * «<9 t · i *« t «í« * »» <ti «» t «« • «t •« t «« t * í [4] YH Hassan, Multiphase Flow Visualization ), 2 ^nd Int. Workschop on PIV, Fukui, Japan 1997. [5] Rebow M., Choi J., LG Chahine, LS Ceccio, Experimental Validation of BEM Code Analysis of Bubble Splitting in Tip Vortex Flow. II ^th International Symposium on Flow Visualization, Notre Dame, Indiana, USA 2004 [6] D. Broder, M. Sommerfeld, Experimental studies of hydrodynamics in a bubble clumn by imaging PIV / PTVsystem. 4 ^th International Symposium on Particle Image Velocimetry Göttingen, Germany 2001 [7] JA Guerrero, F. Mendoza Santoyo, D.

Mfunes-Gallanzi, S Fernandez-Orozco, Particle positioning from CCD images: experimentation and comparsion with generalized Lorenz-Mie theory, Meas. Sci. Technol. 11

568-575, 2000 [8] Y. Pu, X. Song, H. Meng, Off-axis Holographic Particle Image Celocimetry for Particle Flow Diagnosis, Experiment in Fluids, S117-S128, 2000 [9] G. Pan, H. Meng, Digital Holodraphic PIV for 3D Flow Measurement, IMECE2002-33173, New Orleans, Louisiana, November 17-22, 2002 [10] R. Szeliski, SB Kang, Recovering 3D Shape over Motion from Image Streams Using Non-Linear Least Squares. Digital Equipment Corporation, Cambridge Research Lab, Cambridge, Messachusetts, USA 1993 [11] J. Otero, A. Otero, L. Sanchez, 3D motion estiomation of bubble gas in fluid glass, using an optical flow gradient technique extended to a third dimension . Mashine Vision and Application, Vol. 185-19, 2003 [12] K CO Crivelaro, P. Seleghim Jr., Detection of Horizontal Two-Phase Flow Patterns Trough and Neural * 9 • t «

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Mechanical Sciences, Vol. 24, No 1, 2002 [13] C. E. Willert, M. Gharib, Three-dimensional particle imagination with a single camera. Exp. Fluids 12, 353-358, 2002 [14] F. Pereira, M. Gharib, D. Dabiri, D. Modarress, Defocusing digital particle image velocimeters: a 3-component 3-dimensional DPIV measurement technique. Application to bubbly flows, Exp. Fluids S78-S84, 200

SUMMARY OF THE INVENTION

The above drawbacks are largely eliminated by the device for determining the position and / or size of at least one spherical body in the measured fluid space, consisting of a photodetector and an optical system, according to the present invention. It is based on the fact that between the measured liquid and the photodetector there is an optical system whose focal length is different in two planes containing the optical axis.

The optical system may be an anamorphic objective of the photodetector or anamorphic conversion lens located between the photodetector and the measured fluid or a transparent optical quality cylindrical tube in which the measured fluid is located.

The device is preferably provided with a computing device for determining the position and / or size of the body in the measured fluid based on the knowledge of the lens focal length, optical system parameters, refractive indices of individual environments.

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-5a the position of the edges of the half-axis images of the measured spherical bodies relative to the optical axis of the system.

The aim of the solution according to the invention is to determine the position and size of a spherical body or a group of spherical shape bodies in the measured space by means of a single camera - an optical matrix detector. These bodies may be spherical bubbles in the liquid, spherical-shaped droplets in the gas, or directly solid state spheres in both gas and liquid. The principle of the method is to use anamorphic optical system, that is, a system whose focal length is different in two planes containing the optical axis in front of the photodetector. An example of a useful anamorphic system is a cylindrical lens whose focal length is, for example, finite in the sagittal plane and the tangential plane - perpendicular to the sagittal plane, has an infinite focal length.

By reducing the number of cameras required to observe one, the cost of measurement is significantly reduced compared to other stereoscopic measurement methods. Using a conventional radiation source will reduce the cost of measurements compared to methods based on a coherent and diffractive measurement principle, such as light scattering, holographic methods, where the radiation source is a laser. Another advantage is that cylindrical tubes of optical quality can be used directly as an anamorphic member of the optical system, which again simplifies measurement in industrial applications.

BRIEF DESCRIPTION OF THE DRAWINGS

Apparatus for determining the position and / or size of at least one body in a measured fluid space, according to this

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The invention will now be described in more detail with reference to the accompanying drawings, in which: FIG. 1 shows the system in a sagittal plane. FIG. 2 shows the system in a tangential plane. Fig. 3 shows an example of the measured sample. Figures 4 to 6 show schematically in plan view various exemplary embodiments of the device.

DETAILED DESCRIPTION OF THE INVENTION

The device for determining the position and / or size of the at least one spherical body in the measured fluid space is formed by a photodetector provided with an optical system whose focal length is different in two planes containing the optical axis. The measured fluid is in front of the optical system.

In particular cases, the optical system comprises an anamorphic objective of a photodetector or anamorphic conversion lens located between the photodetector and the measured fluid or a transparent optical quality cylindrical tube in which the measured fluid is located.

The device is provided with a computing device for determining the position and / or size of the body in the measured fluid based on knowledge of the lens focal length, optical system parameters, refractive indices of individual environments and the position of the edges of semi-axial images relative to the optical axis of the system.

The experimental arrangement may be constructed, for example, according to FIGS. 1 and 2

Assuming the use of a lens-free lens 1 or knowledge of lens defects 1, in particular distortion, by compensating them, the image of the spherical object will not be circular, but will be elongated at the final focal plane of the cylindrical lens 2 used.

The intrinsic principle of determining the position of a spherical shape object in space and its size is that these parameters can be determined unambiguously by knowing the focal length of the objective 1, the parameters of the cylindrical lens 2, the refractive indices of each environment and

For the actual measurement, standard cameras 2 available as an industrial camera or digital camera can be used. The measurement system may have three different modifications, shown in Figures 4 to 6:

Giant. 4 a standard 2 / f ° ^toa P ^{arat camera} , but with a specially designed lens 1 that is anamorphic.

Giant. 5 a standard camera 31 with a standard lens camera 1 with an anamorphic conversion lens (a separate optical member that provides different views in two planes containing the optical axis) located between the measurement space 4 and the camera lens 2 · Can be mounted directly to the standard lens.

Giant. 6 standard camera 2 / ^Profile P ^Arat the standard lens 2 / ^{wherein the} anamorphic optical element consists of a transparent cylindrical tube 5 in which the optical quality of the medium is monitored spherical objects.

There are some limitations when using this solution. The observation space is limited by the depth (volume) of the sharpness of the optical system used, as • φ φφφφ

-8 Edge of sharp image of the object. The number or size of simultaneously measured objects is limited by the value at which the objects begin to overlap and the position of their edges can no longer be evaluated. The resolution is given by the resolution of the detector (and its software processing inter-pixel iteration, etc.), the quality of the optical elements and the accuracy of their adjustment. The expected resolution is 0.01 mm.

Experiments were performed to measure spherical shape bubbles in water. Bubbles smaller than 1 mm are always spherical in water at normal pressure and temperature. The anamorphic member consisted of a part of a cylindrical tube having an outer diameter of 51.8 mm and a wall thickness of 2 mm filled with distilled water. Using the measuring camera lens with a focal length of 25 mm and a distance of the lens from the measured area of 423 mm, it was possible to evaluate the size, position and subsequent distribution of bubbles in the measured area of 45 mm deep behind the inner tube wall up to a bubble size of 0.2 mm.

Industrial applicability

The device for determining the position and / or size of at least one spherical body in the measured fluid space, consisting of a photodetector and optical system, according to this technical solution finds application especially in measuring the size, position and calculating the distribution of spherical shape objects in space, is applicable in the glass industry for detecting the presence of bubbles in the glass, in the chemical industry - monitoring of bubbles or aerosols in reactors, generally in science and research, but also in the technology of industrial production of beads of all materials.

Claims (5)

PATENT CLAIMS A device for determining the position and / or size of at least one spherical body of spherical shape in a measured fluid space, comprising a photodetector and an optical system, characterized in that an optical system having a focal length in two planes is located between the measured fluid and the photodetector in the mutually perpendicular direction containing the optical axis, different. Device according to claim 1, characterized in that the optical system is an anamorphic objective of the photodetector. Device according to claim 1, characterized in that the optical system is an anamorphic conversion lens located between the photodetector and the measured liquid. Device according to claim 1, characterized in that the optical system is a transparent cylindrical tube of optical quality in which the measured fluid is placed. Device according to any one of the preceding claims, characterized in that it is provided with a computing device for determining the position and / or distribution and / or size of the body in the measured fluid based on knowledge of the lens focal length, optical system parameters, refractive indices of individual environments; the position of the edges of the semi-axes of the images relative to the optical axis of the system.