SURFACE DETERMINATION WITH AN ACCURACY OF FEW MICRONS 
    
  
Karsten Jacobsen 
University of Hannover 
Abstract 
In manufacturing the fine structure of the surface of different objects traditionaly 
will be determined by mechanical profiling 
instruments with direct contact to the 
object. The needle for touching the surface has at least a diameter of Sim and is 
influenced by the inertia and vibrations. In addition some objects with a soft surface 
and for example abrasive wheels cannot be surveyed by this method. With photos 
taken by a stereo microscope, Rolleimetric cameras and CCD-cameras the surface 
determination has been done by photogrammetric solution. The geometric problems 
and the method of solution is described. Accuracies of *t5Uum in the object space can 
be reached. 
Key Words: Macro Photogrammetry, Microscope, Bundle Orientation 
1. Introduction 
The progress in industrial manufacturing with the 
requirement for an exact handling of the different 
steps, without empirical tests, the progress in 
medicine and other areas is causing a growing 
demand also for an accurate information about 
the threedimensional shape of the handled objects. 
For many purposes there is a request for 
informationaboutthe fine structure of the surface. 
By tradition in the manufacturing mechanical 
profiling instruments are used. But they are 
limited to profiles, they are sensitive about 
vibrations and it is not possible to examine soft 
surfaces or objects like abrasive wheels.In addition 
the needle for touching the surface has a diameter 
of at least 5um and is influenced by the inertia. 
As alternative solution the surface determination 
by photogrammetry can be used. Corresponding 
to the required fine structure, a large photo 
scale has to be used. The handling of images with 
a scale between 8 : 1 and 1 : 10 will be descriped. 
Photos or digital images (CCD-cameras) can be 
used. 
2. Camera Systems 
The imaging has been done with different optical 
systems. Metric cameras are not availble for the 
extreme close range - the macro photogrammetry, 
so nonmetric or partial metric cameras had to be 
used. 
2.1 Stereo Microscope 
Stereo microscopes are often used in medicine. 
The handling is very simple, a direct stereoscopic 
view to small objects is possible and after fast 
changing of the lenses against camera tube, 
stereoscopic photos can be made. The image 
scale and the focus can be changed. 
  
  
object 
  
Fig. 1: stereo microscope - geometric situation 
A standard film for images 36mm * 24mm will be 
used. For 3.5-times enlargement the calibrated 
focal length will be f=384mm. If the usual 
configurationofthenormalcaseofphotogrammetry 
would be used, with 60% endlap the base in the 
photo would be 14.4mm - corresponding to a base 
to distance relation of 1:27. With such a relation 
the stereo view would be very poor. By this reason, 
the principal point is shifted 50mm in the direction 
of a base enlargement. Together with a 100% 
overlap of the photos, the base has a size of 
100mm in the image plane, that means, the base 
to distance relation will be 1:3.8. 
2.2 Partial Metric Cameras 
Alternatively to the stereo microscope cameras 
with macro lenses, adapter rings and 
teleconverters can be used. For a sufficiant 
photo scale the Rolleimetric 6006 and 3003 have 
been used with a calibrated focal length between 
50mm and 600mm. The base to distance relation 
for the normal case is not sufficiant, by this 
reason the cameras have been used oblique.