Laser Triangulation a photodetector. As shown in Figure 1, a diode laser is used to generate a collimated beam of light that is then projected onto a target surface. A lens images the spot of reflected laser light onto a photodetector, which generates a signal that is proportional to the spot's position on the detector. As the target surface height changes, the image spot shifts due to the parallax. To generate a three-dimensional image of the part surface, the sensor scans in two dimensions generating a helical set of radius data that represents the inside surface topography of the tube.
Software then generates a user friendly color graphical image of the inside surface of the tube.
A laser profilometry inspection system has the ability to acquire substantial quantities of inspection data in a very short period of time. Of course, large data files of this sort must be manageable and easy to analyze for any substantial benefit to be gained from them. Software has been designed which automatically compresses and arranges the data for easy viewing and quick analysis processing making the initial large data files a non-issue. These custom laser-mapping probes were designed to inspect catalyst tubes prior to being placed into service or during a catalyst change out. Access to the interior of the tube is essential since the laser-mapping probe must pass through the tube to gather the ID information.