Al-Hanbali, Nedal 
of the lab testing results, which proves that the system can measure deformations very precisely. The final section 
concluded the results of the testing presented to assess the use of the LSS for deformation measurements. 
2. THE LASER SCANNING SYSTEM 
The LSS technique is a dual-axis laser scanner based on an 
auto-synchronized triangulation scanning scheme that is 
patented to the National Research Council of Canada 
(NRC), NRC report(1993) and Rioux (1994). The system 
provides fast and reliable three-dimensional deformation 
measurements and can measure objects between 0.5 m to 
100 m with a field of view of up of 36° X 40°, Beraldin et. 
al. (1992,1993). The system provides two output images: 
an intensity image and a depth coded image. The LSS can 
provide control over the scanned area and depth, which 
makes it a flexible system to use. For example, the 
operator can specify the image resolution, the scanned area 
within the maximum field of view, the suitable laser power 
for a specific surface, and the scanning mechanisms, Blais 
et. al. (1986, 1991) and Beraldin et. al. (1994). The system 
consists of a laser camera connected to a control panel, 
laser generator, and computer system running OS9 
operating system, see Figure 1. 
  
Figure 3: Dual-axis synchronized scanner in 
schematic representation (from Beraldin et. al., 1993). 
  
Figure 1: The Laser Scanning System 
Range Resolution 
    
  
Surfaces 
  
  
of Opaque 
Objects 
in Scene 
     
Range 
Imaging 
Sensor 
     
  
  
  
   
Angular 
Field of 
View 
X-axis 
  
    
Standoff Distance Depth of Field 
     
  
  
   
Scanning Mirror 
(Deflector) 
Projection 
Angle : 
/ s Z-axis 
— I 
   
  
Figure 2: (b) Optical arrangement of the active 
triangulation principle 
The basic geometry of the scanner camera (range 
sensor) in two-dimensions is shown in Figure 2a, the 
scanned field of view, the detected depth distance r, and 
the angular field of view are also shown in the figure. 
Figure 2b illustrates the optical arrangement principle 
of a triangulation range-sensor and the projection of a 
scanned point on the position sensor of the laser 
camera. 
The dual-axis-synchronized scanner, shown in Figure 3, is based on the Auto-synchronization approach and the 
Sheimpflug condition Rioux (1984). Auto-synchronization means that the projection of the laser spot and the deflection 
of the detection axis are synchronized automatically by using one rotating mirror and two fixed mirrors. The rotating 
mirror is silver-coated on both sides while the fixed mirrors are silver-coated on the front, Figure 3. For more 
information see Al-Hanbali (1998) and Al-Hanbali et. al. (1999). 
The dual-axis laser scanner is shown schematically in Figure 3. Assuming that the scanner is set up (on a tripod for 
example) with the axis of the pulsed laser aligned vertically. The X-axis scanner (i.e., the galvanometer) measures the 
  
10 International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B5. Amsterdam 2000. 
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