Transmitted Wavefront Metrology on Large Domes and Windows

There is a need for economical fabrication of hemispherical missile domes. An essential, and unsolved, part of the fabrication process is the fast and accurate measurement of the transmitted-wavefront error of the dome over its full aperture. In the proposal we describe in detail two different approaches to solving the transmitted-wavefront measurement problem. Key to both approaches is an innovative optical layout such that the required null optic is small and modest cost in one case and very low-cost in the other. Additionally, both approaches use variations of existing data reduction algorithms, which minimize the development risk. One approach uses interferometry to measure the entire aperture in double-pass without stitching and is configured in a manner that is relatively insensitive to alignment of the dome to the instrument. The second approach scans a small aperture of the dome using rotary motion measuring the wavefront tilt in double-pass and then integrating the data to obtain the transmitted wavefront. The goal of the proposed work is to evaluate the expected performance of the two concepts and to select the approach most likely to meet measurement performance, ease-of-use and cost requirements.