88 
2.2 The photogrammetric front end 
The three cameras of the photogrammetric observation module are fixed on a common frame with their relative positions 
chosen with respect to the size of the observation window and the depth of the scene to be observed. Such a 
photogrammetric observation module can be used for measurements on different types of experiments. It can be 
exchanged with other diagnostic tools and because it is applied from one side only can even be used simultaneously with 
other diagnostic tools like interferometry for example. 
  
  
  
  
  
  
  
Figure 3: The flexible concept of the testing platform: here the calibration testfield 
Instead of the fluid cell, a testfield can be mounted in front of the measuring head for a precise automatic calibration of 
the camera setup. This concept of exchangeable, reconfigurable measuring heads together with also exchangeable 
experiment cells gives highest flexibility concerning the different types of experiments to be expected (see fig. 3). 
As camera and image processing hardware, three PULNIX TM 9700 fullframe digital CCD cameras connected to a MVFG 
Video frame grabber from MIKROTRON are used. The cameras have an asynchronous electronic full frame shutter and 
onboard frame memory, so three images of the scene can be acquired simultaneously with very short acquisition times. 
This is necessary for the precise three-dimensional measurement of moving scenes. The frame grabber is connected to 
the CPU main memory via a fast video link and the images can be processed immediately after image acquisition directly 
in CPU main memory. 
3. CHARACTERIZATION OF THE BREADBOARD 
For the determination of the position and the shape of drops and columns in a fluid matrix some characteristics of the 
breadboard and the photogrammetric front end have to be determined. The imaging hardware including the cameras and 
the frame grabber are to be calibrated to describe the projection errors. Several geometrical quantities of the fluid cell 
have to be defined as well. 
3.1 Determination of the cell geometry 
To evaluate experiments in the described fluid cell, a three-dimensional Cartesian coordinate system has to be installed. It 
is defined by the réseau crosses on the front and back window of the fluid cell. Therefore the coordinates of these crosses 
and the coordinates of control points on the front side of the fluid cell, which are used to orientate the camera head in the 
cell coordinate system, have to be determined. 
IAPRS, Vol. 30, Part 5W1, ISPRS Intercommission Workshop "From Pixels to Sequences", Zurich, March 22-24 1995 
  
pr 
to 
be 
af 
pl 
or 
fre 
te 
ar 
TI 
te: 
Th 
ca 
JA