Aspheric Figure Metrology Using a Laser Unequal-Path Interferometer with Computer-Generated Holograms

We propose an innovative CGH-LUPI interferometer for high accuracy figure metrology of deep aspheric optics. The CGH-LUPI will use CGH-compensated Twyman-Green mode for testing of deep aspherics, but will operate equally well in normal Twyman-Green and Fizeau modes. It will differ significantly from previous aspheric interferometers in two key aspects. First, its elegant simplicity will allow easy operation and independent verification of all aspects of system calibration. Second, the proposed instrument will use affordable photomask quality CGH nulls to produce aspheric wavefronts which are everywhere perpendicular to the test optic. In a Phase I program, we propose to complete a detailed optical and preliminary mechanical design of proposed instrument. We also propose construction of a breadboard optical model to demonstrate several key features of the CGH-LUPI interferometer.