High-accuracy three-dimensional aspheric mirror measurement with nanoprofiler based on normal vector tracing method

- High-precision free-form surface measurement with a nanoprofiler is demonstrated.
- Optional uncertainty components like reference surface are not included the nanoprofiler.
- Sub-nanometer repeatability of aspheric surface measurements was achieved.
- Three-dimensional measurement is achieved with small radius curvature aspheric surface.
- The nanoprofiler and interferometer results agreed to within the systematic error.

The demand for high-accuracy aspheric optical elements has increased significantly in recent years. The surface shapes of such optical elements must be measured with 1 nm Peak-to-Valley(PV) accuracy; however, it is difficult to achieve 1 nm PV accuracy with conventional methods. In this research, we developed a nanoprofiler based on the normal vector tracing method that can achieve the required accuracy. An aspheric mirror was measured by using the nanoprofiler, and repeatable, sub-nanometer measurements were achieved. Furthermore, we compared our nanoprofiler results with those of a Fizeau interferometer and found that the difference was within the systematic error.