Scanning SCOTS Measurements for Corrective Optics

We propose to develop an optical system to measure arch-shaped corrective optics using the Software Configurable Optical Tests System (SCOTS) developed by the proposing team for freeform aspherics. The full arch is measured by scanning subaperture regions and stitching the data. SCOTS measurements use video images of an optic under test illuminated with modulated patterns from a digital display. Powerful software and careful calibration provide measurements of wavefront slope with sub-microradian precision. The slopes are integrated to provide surface topology. We will apply this robust new technology for measuring the optical effect of light transmitted through subaperture regions on the corrector optics. These measurements are scanned and stitched together to provide a measurement of the full arch-shaped optic. The large dynamic range of the SCOTS test accommodates the complex shapes and many degrees departure from parallelism. Carefully calibrated cameras provide simultaneous measurements of both surfaces with microradian slope resolution. The advantages of this system are clear. A 25-mm wide, 100-mm tall arch freeform aspheric corrector can be measured in a few minutes with 20 nm accuracy. Furthermore, this measurement technique can be readily extended with the addition of a roll axis for measuring high aspect domes.