White-light vertical scanning technique has been used for surface topography measurement because of its characteristics
of non-contact, high-accuracy and large range. In this technique, PZT is usually employed for high resolution vertical
scanning. Due to the nonlinearity and creep characteristics of PZT however, large scanning positioning error is inevitable
if direct interference image sampling without positioning metrology is adopted. Otherwise if positioning metrology is
adopted for every image sampling, measurement efficiency will be reduced greatly. To solve this problem in this paper,
the nonlinearity characteristic of PZT is analyzed and its local linearity is investigated, and based on the local linearity a
novel interference image sampling strategy is proposed. In this strategy, the whole scanning range is divided into many
sub-ranges, in which the non-linearity errors are small enough for direct interference image sampling. When white-light
vertical scanning measurement is conducted, in every sub-range, interference images are sampled directly at every
scanning position corresponding to equal driving voltage interval of PZT, while the end points of each sub-range are
measured by a positioning metrology system. Thus based on the local linearity of sub-range, the scanning positioning for
image sampling can have enough accuracy, while less positioning metrology is needed for high measurement efficiency.
Analysis and case study proves the improved scanning positioning accuracy and measurement efficiency through the
novel sampling strategy.