Novel hybrid stylus for nanometric profilometry for large optical surfaces.

We report a new plunger and pivot hybrid stylus system suitable for point-by-point form measurement for large optical surfaces up to 1m in diameter. The geometric stylus model was established to predict the height measurement error. The 'Height Difference Variation (HDV)' technique was developed for minimizing the stylus pivot motion error. The laboratory stylus system exhibited the repeatability of less than 10 nm for up to 8.1 degrees in slope and the form departure of 26 nm from the calibration sphere. The hybrid stylus may offer an efficient form metrology solution to the mass production of optical surfaces of 1-2m in diameter.