127 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
100000. - 
ng . 
re = 10000. 8 : 
he a e Delft wind 14 m/s depth 5 cm 
& 1000. ’ , * Delft wind 11 m/s depth5cm 
= gel ario C] Marseille wind 14 m/s. depth 5 cm 
2 : yw | O Marseille wind 13 m/s depth 5 cm 
7) 5 100. =e measurements in Marseille 
: = "lll are taken by [Baldy,85] 
— e ® 
S 10 e : 
g; # 
1 " n 
8) 0.05 0-3 dius (ifn) 0.5 
Figure 5: Size distribution of bubbles measured at a wind speed of 14 ms and 5cm below the mean water surface 
p in the wind/wave flume of Delft Hydraulics, The Netherlands. 
6 CONCLUSIONS 
In this paper it has been showed that depth-from-focus techniques can be used with only one image provided 
of that a precise knowledge of the shape of the object is known and that an adequate illumination and low-level 
image processing has been performed. The size and the distance of bubbles from the focal plane could be 
measured from only one image. Bubbles are quite simple objects in the sense that they have an elliptic 
ed shape. Although we have demonstrated the technique only with these simple objects, we feel that it opens 
the way to further research in one-image depth-from-focus. Counting cells in bioreactors is already another 
jus 
no successful application of a different one-image depth-from-focus technique developed in our research group 
ico by [10]. The next logical step of research would be to extend these techniques to more complex and general 
object shapes. 
ACKNOWLEDGEMENTS 
Financial support by the National Science Foundation (OCE89 11224), the Office of Naval Research (N00014-89-J- 
D 3222), and the European Community (Large Installation Program) is gratefully acknowledged. 
REFERENCES 
s [1] Baldy, S., Bouruel M.: 1985, ‘Measurements of Bubbles in a Stationary Field of Breaking Waves by a Laser Based 
of Single-Particle Scattering Technique’ Journal of Geophysical Research, Vol. 90 No. 1 
ch [2] Darell, T., Wohn, K.: 1990, ‘Depth-from-focus using a pyramid architecture’, Pattern Recognition Letters, 11, 
ng 787—796 
is [3] Ens, J., Lawrence, P.: 1993, ‘An investigation of methods for determining depth-from-focus’ , IEEE Trans. PAMI, 
It 15, 97-108 
[4] Farmer, D. M., McNeil, C. L., Johnson, B. D.: 1993, ‘Evidence for the importance of bubbles in increasing air-sea 
gas flux’ , Nature, 361, 620-623 
[5] Geißler, P., Jähne, B.: 1994, ‘An Imaging Optical Technique for Bubble Measurements’, 3rd international meeting 
on natural physical processes related to sea surface sound, Lake Arrowhead, CA 
. [6] Hering, F., Merle, M., Wierzimok,D., Jáhne, B.: 11995, ‘A Robust Technique for Tracking Particles over Long 
m Image Sequences’, to be published in Proc. of ISPRS Intercommission Workshop 'From Pizels to Sequences', Zurich, 
t 8 q ? Dp 
> March 22 - 24. In Int'l Arch. of Photog. and Rem. Sens., Vol 30, Part 5W1 
3 5 [7] Lamarre, E., Melville, W. K.: 1991, ‘Air Entrainment and dissipation in breaking waves’, Nature, 351, 469-472 
he [8] Lai, S. H., Fu, C. W., Chang, S. Y.: 1992, ‘A generalized Depth Estimation Algorithm’, IEEE Trans. PAMI, 14, 
: 405-411 
ent 
[9] Pentland, A. P.: 1987, *A new sense for depth of field', IEEE Trans. PAMI, 9, 523-531 
[10] Scholz, T., Jáhne, B., Suhr, H., Wehnert, G., Geifiler, P., Schneider, K.: 1994, *A New Depth-from-Focus Tech- 
nique for In Situ Determination of Cell Concentration in Bioreactors', Proceedings of the 16th DAGM Symposium, 
Wien, 145-154 
5 IAPRS, Vol. 30, Part 5W1, ISPRS Intercommission Workshop “From Pixels to Sequences”, Zurich, March 22-24 1995