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Measure/Headtest Screen B
Measure/Headtest Screen B is a display from a rougher surface, Ra of about 30 microinches. Because the
surface is relatively rough, the specular beam is now lost as it bounces off the surface into Lasercheck.
There is no obvious large voltage anywhere in the array. The standoff reading indication is no longer
reliable. On these rougher surfaces, we cannot do height alignment with Lasercheck’s help. What must be
done is to either align on a smooth surface in the exact position the rough surface is at or make the rough
surface look smooth to Lasercheck for just the alignment. A reliable way to make a rough surface look
smooth to Lasercheck is to wipe a thin film of oil on the surface. This makes the surface look “slick” to the
human eye and to Lasercheck. Position the oiled portion of the surface under Lasercheck and proceed with
the vertical alignment using the Measure/Headtest to position the specular center on detector # 6.
It is important to perform this alignment at least once because the signals from a well-aligned rough surface
can be identical to signals from a misaligned smooth or rough surface. You must be certain Lasercheck is
aligned to rely on “rough” surface measurements.
