Surface metrology with a stitching Shack-Hartmann profilometric head

In this article, a stitching Shack-Hartmann profilometric head is presented. This instrument has been developed to answer improved needs for surface metrology in the domain of short-wavelength optics (X/EUV). It is composed of a highaccuracy Shack-Hartmann wavefront sensor and an illumination platform. This profilometric head is mounted on a translation stage to perform bidimensional mappings by stitching together successive sub-aperture acquisitions. This method ensures the submicroradian accuracy of the system and allows the user to measure large surfaces with a submillimetric spatial resolution. We particularly emphasize on the calibration method of the head; this method is validated by characterizing a super-flat reference mirror. Cross-checked tests with the Soleil's long-trace profiler are also performed. The high precision of profilometric head has been validated with the characterization of a spherical mirror. We also emphasize on the large curvature dynamic range of the instrument with the measurement of an X-ray toric mirror. The instrument, which performs a complete diagnostic of the surface or wavefront under test, finds its main applications in metrology (measurement of large optics/wafers, post-polishing control and local surface finishing for the industry, spatial quality control of laser beam).