Self-Aligning Scanning Shack-Hartmann Sensor for Automatic Wavefront Measurements of High-NA Optics

Optical parts, such as lenses or mirrors, are often qualified by surface shape metrology. Wavefront measurements allow for a more direct measurement of the performance of an optical part. However, the dynamic range of current wavefront sensors is not sufficient for measuring the wavefront generated by high-NA optical parts. In this paper, a wavefront sensor is combined with a mechatronic positioning system to overcome these limitations by repositioning and reorienting the wavefront sensor. Feedback loops are implemented to ensure a tangential orientation of the wavefront sensor in every measurement position. An experimental setup is constructed and a measurement strategy that compensates for tip and tilt between wavefront and sensor is developed. It is demonstrated that this setup is capable of directly measuring the wavefront of a high-NA optic.