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Fig. 11 and Fig. 12: Corresponding images taken with left and right camera. 
S. DSM GENERATION 
DSM is the digital tooth model. The purpose of DigiDent is the measurement of three dimensional position and rotation changes 
of every single tooth. The generation of a complete DSM is not necessary on principle. Theoretically geometric parameters of 
position and rotation changes can be derived by estimating transformation parameters using four or five homologous points on 
every tooth at different time periods. Since no points that can be detected as homologous points can be marked on the teeth a 
different solution has to be found. Therefore a DSM of every tooth is generated. Transformation parameters are derived by 
comparing the DSM at two different time periods. 
For DSM generation until now only image data acquired from a dental test model was used, since questions of illumination have 
not been solved until now. However, the same configuration of teeth, mirror and cameras was used. Imagery was acquired 
sequentially with only one camera and one frame grabber, since only one imaging system had to be calibrated. Figures 13 and 14 
show imagery acquired from the model without special illumination. The crosses on the mirror surround the teeth. Since the 
crosses have a line width of only 2-3 pixels they cannot be seen very well in the figures shown below. 
es 
  
Fig. 13 and Fig. 14: Stereo pair taken from the dental test modell. 
5.1 ORIENTATION OF IMAGES 
Images are oriented by measuring the crosses in left and right image. They shall be detected automatically (at the moment they are 
measured semiautomatically using least squares template matching) and measured by least squares template matching. Using 
bundle adjustment unknowns of exterior orientation are estimated. The reliabilty of the elements of the exterior orientation is very 
important, since geometrically constrained least squares template matching is applied for DSM generation. Therefore weakly 
matched crosses have to be detected automatically. Robust estimation models have to be impiemented when crosses are detected 
and measured automatically in the future. : 
IAPRS, Vol. 30, Part 5W1, ISPRS Intercommission Workshop “From Pixels to Sequences’, Zurich, March 22-24 1995