A novel profilometer for three-dimensional (3D) surface topography measurement is
presented. The profilometer has large measuring range, high precision and small measuring touch
force. It is composed of a two-dimensional (2D) displacement sensor, a 3D platform based on
vertical scanning, measuring and control circuits and an industrial control computer. When a
workpiece is measured, the vertical undulation of the profile at a sampling point leads to a zero
offset of the 2D displacement sensor. According to the zero offset, a piezoelectric actuator and a
servo motor drive the vertical scanning platform to move vertically to ensure that the lever returns
to its balance position. So the non-linear error caused by the rotation of the lever is very small even
if the measuring range is large. When the stylus barges up against a steep wall, the horizontal
resistance force results in another zero offset of the 2D displacement sensor. If the zero offset
exceeds a quota, the vertical scanning platform descends to make the stylus climb the steep wall
successfully. According to the theoretical and experimental analysis, the profilometer can measure
roughness, profile of sphere, step, groove and other 3D surfaces with curvature precisely.
