Evaluation of concave seismic isolator surfaces using LCD null-screens

The sliding seismic isolator industry requires new metrology technologies in the manufacture of concave surfaces to ensure high-precision geometries, which are essential for guaranteeing controlled friction behavior and predictable dynamic performance. In this work, we present a novel, to our knowledge, null-screen method that uses programmable dot patterns to characterize both the global shape and local defects of these surfaces in a single-shot regime. To validate the approach, experiments were conducted on two prototypes of sliding surfaces. We detail the integration and alignment of the test system to extract the geometric parameters that describe the evaluated surfaces. Measurements revealed deviations of less than 1% in the radius of curvature relative to the design surface, along with root-mean-square (rms) differences in surface shape less than 102 µm.