Influence of specimen positioning stage drift in tilted-wave interferometry for accurate form measurements for aspherical and freeform surfaces

Accurate form measurements for aspherical and freeform surfaces are in high demand and tilted-wave interferometry is a promising method to fulfill this need. However, interferometric form measurement methods for curved surfaces are sensitive to positioning errors of the surface under test, especially along the optical axis. To investigate the influence, we have measured the drift of two different positioning hexapods and simulated the influence of the drift on the form reconstruction of the surface under test. The simulation results were compared to repeated form measurements of a surface under test with the tilted-wave interferometer.