Pitch, roll, and null

The lateral/Y axis, or pitch axis is an imaginary line running horizontally across the sample through the center of gravity. A pitch motion is an up-or-down movement of the front or back of your sample as mounted on the stage.

The longitudinal/X axis, or roll axis is an imaginary line running horizontally though the length of the sample through its center of gravity. A roll motion is a side-to-side movement or tilting left or right of your sample as mounted on the stage.

To "null" the fringes is to adjust the pitch and roll of your sample so it is parallel to the plan of the interference fringes, which is perpendicular to the Z-scan axis.

Nulling the fringes predominantly helps you with minimizing the scan length needed to measure your surface.

Nulling pitch and roll; The surface on the left is not nulled. The scan length required to get information from the entire surface is roughly 4 times that of the nulled surface on the right. This is because the left hand side needs a scan length that accounts for the sample tilt and roughness whereas the right side needs a scan size just for the sample roughness.

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