Effects of a laser beam profile to measure an aspheric mirror on a high-speed nanoprofiler using normal vector tracing method

In order to develop the next generation of ultraprecision aspheric mirrors, a high-speed nanoprofiler is indispensable. We have developed a new version of such a nanoprofiler by tracing the normal vector of a mirror surface. The profiler is based on the straightness of laser light without the use of a reference surface. Any aspheric mirror can be measured within a few nm. This nanoprofiler measures the normal vectors and their coordinates on the surface of a mirror. Each normal vector is determined by making the incident light path and the reflected light path coincident, which is done using two sets of two pairs of goniometers and a straight stage. The profile is calculated using the measurement points and the normal vectors on the surface. In this paper, we simulate and measure the effects on a laser beam profile in order to measure an aspheric mirror with a high-speed nanoprofiler using normal vector tracing. Taking the effects on the beam profile into consideration is required to measure profiles of aspheric mirrors within an accuracy of 1 nm.