A second-generation constant force profiler is described combining a c
apacitance based stylus force probe with interferometric optical metro
logy to monitor position of the specimen carriage. The probe has a ver
tical range of 15 mum with a resolution of 0.23 nm and a flat bandwidt
h response with a -3 dB cutoff at 228 Hz. Passing the output signal th
rough a single pole 200 Hz low-pass filter, an overall system peak-to-
peak broadband noise of less than 5 nm is observed. Manufactured prima
rily from inexpensive materials, the instrument demonstrates a stabili
ty of around 1 nm min-1 under controlled laboratory conditions. Using
an inexpensive motor/gearbox/micrometer open-loop drive with velocity
variations of up to 20%, profiles showing nanometer repeatability over
15 mm traces are demonstrated. Also shown is a profile of a soft cont
act lens in the hydrated state. The effect of the contact stiffness on
the stylus probe/specimen interaction is illustrated by examining the
dynamics of the force probe system while operating in the repulsive m
ode.