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ina 1996 
THE OPTICAL TUBE MEASUREMENT SYSTEM OLM 
- PHOTOGRAMMETRIC METHODS USED FOR INDUSTRIAL AUTOMATION AND PROCESS CONTROL 
Werner Bósemann 
AICON-Industrial Photogrammetry and Image Processing 
Bültenweg 23 
D-38106 Braunschweig 
Tel.: ++49 / 531 / 34 45 01 
Fax: ++49 / 531 / 34 45 04 
KEY WORDS: Industry, Metrology, Automation, Change Detection, On line, Quality, Production Control 
ABSTRACT 
Qualitiy control and inspection has become a major tool in industrial production. New measurement systems have to 
be developed to fulfil these control mechanisms without interfering the production process. Because of the necessity of 
non interfering systems those have to be contactless. These requirements can be fulfilled by optical measurement 
systems. 
The following paper will show an example of such an optical measurement system for measuring spatially bended 
tubes.There are numerous tasks to measure tubes for shape control in the industrial process. Tubes with different 
bends, curves and straight parts have to be compared with CAD data. These tubes could be flexible and therefore 
difficult to measure mechanically. The main problem is to fix the tubes. Another requirement is a short measurement 
time for shape control in the production line. 
This new measurement system is specially designed for 3-dimensional measurement of tubes. The features of the tube 
measurement system are: non contact measurement, no elastic deformation of the tubes by the fixture, fast acquisiton 
tube geometric, flexible fixing unit, short measurement time by using digital image processing, variable measurement 
volume and high accuracy. 
1. INTRODUCTION 
The optical tube measurement system OLM is a system, 
which allows a contactless measurement of spatially 
bended tubes. Such spatially bended tubes are an 
important component of different industrial products like 
brake tubes or gas tubes from automotive or aircraft 
industry, or hydraulic tubes and refrigerant tubes from 
mechanic engineering and plant construction. 
The OLM is an opto-electronic measurement system 
based on CCD-cameras, working on principles and 
algorithms of digital image processing and close range 
photogrammetry (Schneider, Sinnreich, 1990, 1992). The 
optical tube measurement system (OLM) is a powerful 
tool for a fast and precise 3-dimensional reconstruction 
of tubes of different types and shapes. 
It is integrated in the production line via a computer 
network for online process and quality control. 
2. SYSTEM CONFIGURATION 
The measurements are performed in a socalled optical 
measurement cell. Several electronic cameras are 
mounted to a fixed frame, images from different views of 
the tube to be measured can be taken. The cameras are 
connected to a common PC as control unit. The 
illumination can be chosen either toplight or backlight. 
2.1 Optical measurement frame 
The mechanical construction consists of a stable ground 
plate and an aluminium frame which is connected to the 
ground plate and serves as camera fixture. On the white 
ground plate circular reference targets are marked in a 
regular raster. Additional reference marks are positioned 
on steal bars at the border of the measurement volume. 
These side points are necessary to perform a precise 
calibration of the camera configuration. The arrangement 
of the reference marks and the camera figures are shown 
in figure 1. Both sides, the back wall and the ceiling of 
the surface are closed to protect the cell against dirt and 
interfering external lights. 
| aluminium frame | camera | 
\ 
conrtol unit 
AN 
3 
| ground plate - parts luis 
  
    
      
   
              
  
  
e fl e | © e n e A 
1 
| 
reference points | tube 
  
  
  
Fig. 1: Optical measurement cell 
The illumination of the measurement volume is realised 
by neon tubes mounted on the ceiling of the measuring 
cell. For a homogeneous illumination of the measuring 
volume a milk glass plate is mounted infront of the 
flourescent tubes. Such a top illumination has the 
disadvantage that only dark and not specular reflecting 
tubes can be measured in front of the white ground plate. 
Metallic surfaces will show disturbing reflections in the 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B5. Vienna 1996