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Lasercheck Alignment Principles and Procedures
This section contains information on principals and procedures to install and align Lasercheck heads. The
keys to getting accurate and repeatable data are controlling alignment and cleaning the surface.
How Does Lasercheck Work?
The visible (650-nm.) laser illuminates the surface with a shallow incident angle to measure surface
roughness features. The distribution of reflected and scattered light from the surface is detected by a
photodiode array with 35 small closely packed detectors. This relative distribution of reflected and scattered
light is used to calculate the surface roughness of the area illuminated by the laser beam. The array is also
scanned by software to find the specular beam (when there is one) and its position is used to determine
height of the measurement head from the surface.
Figure 6 - Schematic Diagram of Lasercheck Instrument
Figure 6 shows a schematic of the layout of the laser, the beam path and the detectors in Lasercheck. The
“Photodiode Array” has 35 discrete detector elements. Of the 35 detectors in the array, only the 24 detectors
that are positioned to the “inside” of the specular laser beam (toward the direction of the incoming laser
beam) are used. This is important to understand in the discussion of alignment.
Laser
Detectors
Specular
Scatter