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Research projects

Drop Volumetry by Vision

José Gonzalez

Keywords

Machine vision, metrology, drop volumetry, drop flow measurement

Purpose of the project

This project deals with the liquid flow measurement for the medical environment, where several constraints set a limit to the wide spectrum of flow measurement methods and where drop counting is used at a large scale, although it is not precise. The goal of this project is to evaluate the feasibility of improving the measurement accuracy of drop flow devices by imaging and to estimate the obtainable accuracy in the perspective of developing newer and more accurate drop flow devices

Performed work and results

Drop volume measurement by vision is considered in the context of liquid flow metrology. It requires to record the silhouette of a falling drop and to estimate from it the unknown volume. Three volume computation algorithms derived from geometric features of figure 1 were defined and compared.

First experiments reveal typical drop shapes. The drop shape varies veries in time in a wide scale as illustrated in figure 2

Fig. 1 Geometric features of the observed drop silhouette Fig. 2 Drop shape variation

Further series of experiments compare the computed volume obtained by vision of single drops with their volume obtained by weighting. The results reveal that simpler methods are clearly inefficient while the advanced method performs well. It reaches an rms-error below 1% in normal measurement conditions. These figures speak for the interest of the measurement by vision and represent a good base for predicting the suitability of the method in various applications.

References

H. Hügli & J. Gonzalez, "Drop volume measurement by vision", Imaging 2000, SPIE Electronic Imaging Conference, San Diego, Jan 2000, Vol 3966-11, pp. 60-66

hu / 23.05.2005
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