Al-Hanbali, Nedal
Image processing techniques are well developed for conventional and CCD cameras. Due to the research environment,
the author developed this software re-addressing image processing techniques and making use of the wide dynamic
range of the LSS images (i.e. the digital pixel value of the LSS images is a two byte value), see Obidowski et. al.
(1995). The software is used for the local scaling approach and for the calibration purposes. Figures 5a and 5b show
some of the functionality of this software.
To illustrate the use of the software, Figure (5a) shows the top view of a typical industrial setup (Al-Hanbali 1994 and
1998). Figure (5a) shows the platform of the Image Tools software. The upper image is the intensity image displayed in
gray values and the lower image is the depth-coded image. As shown in the color palette box, the colors represent
scaled ranges (i.e. distances from the camera position to surface points in the scene). The upper right dialog box shows
the different tools used to process laser images.
4 LOCAL SCALING APPROACH
4.1 Lab Testing:
To demonstrate the local scaling approach, a mechanical test rig shown in Figure 5 is scanned before and after
introducing movement, producing for each case a depth coded image and an intensity image. Figure (5b) shows the
result of scaling the direct difference between two depth-coded images. The upper left image in the Image Tools
platform figure shows the surface movements displayed in colors. The movement values for each color are displayed in
the color palette in centimeters. A profile of these movements along a cross-section is shown at the lower left side. For
further details regarding the method see Al-Hanbali (1998).
The precision of measurements obtained from lab testing using this approach found to be equivalent to the expected
precision of the LSS derived from the mathematical model for calibration purposes, (Al-Hanbali and Teskey 1994, AI-
Hnbali 1998). Two test were conducted (one using a Static test rig and the other using Motorized test rig) applying
approach. The precision of measured introduced movements were as follow: 0.2 mm for a depth distance of 0.75 m and
1.0 mm for a depth distance of 1.75 m. The expected precision of each are 0.15mm an d 0.85 mm, respectively.
4.2 On-Site Testing:
on-site test was carried out at the Sheerness Generating Station, Alberta, Canada. Figure 6 illustrates the machinery
coupling of the turbine-generator combination, its intensity and depth coded images, a sphere mounted on a 2-d
translation stage and sphere mapped image (mapping is done by NRC). The sphere and the retroreflective targets,
shown in the figure, are used as reference points. The on-site testing was conducted in an environment of high
temperature (about 40°C) and high vibration.
0 25 so 75 10!
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Figure 6:(a) The machinery coupling, the retro-reflective targets and a sphere mounted on a 2-D translation stage. (b)
Three-D mapping of the sphere and the translation stage. (c) Depth coded image of the machinery coupling, the retro-
reflective targets and the 2-D translation stage. (d) The flange's approximate dimensions in millimeters.
Figure 7 shows the measurements and the RMS values of the intorduced movements of the sphere compared to the
actual movements. Measurements are based on scaling two picked areas from the digital image. Area I is part of the
sphere surface and area II is part of the surface of the 2-d translation stage (the moved part).
The achieved precision ranges from 0.20 mm when small deformation are introduced (up to 2.0 mm deformations) to
0.35 mm for large deformations (up to 50.0 mm deformations). The expected precision of the LSS derived from the
mathematical model for calibration purposes is about 0.18 mm, see Al-Hanbali (1994) and Al-Hanbali and Luarent
12 International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B5. Amsterdam 2000.
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