Chapter 9 Flatness Measurements
Positioning the Laser Head
9-20 Measurements Reference Guide
Positioning the Laser Head
After you assemble and mount the optics, you must position the laser head
and place the straightedge along the first measurement line.
NOTE To ensure that you can properly set up the optics, the straightedge you use
must be long enough to extend past the ends of the diagonals, or you may
need more than one straightedge. This allows you to position the
interferometer outside of the measurement grid.
Follow these steps:
1 Position the laser head along your first measurement line.
When positioning the laser head, follow these guidelines:
• If you can align the laser head with a measurement line, choose a line
and position the laser head so it points along the line (Figure 9-10).
Although Figure 9-10 uses the center line as an example, you can
choose any line.
• If you cannot align the laser head with a measurement line, choose an
edge and position the laser along it (Figure 9-11). Visually align the
laser head so the laser beam is approximately 25 mm (1 inch) above
the edge of the surface plate. The 25 mm (1 inch) gap leaves room to
properly position a flatness mirror. After you have assembled and
mounted the optics, you will adjust the laser head more precisely.
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