Holographic shearing interferometry and its implications for freeform characterization

This work explores combining the reference sphere and nulling hologram for freeform measurements by using a nulling reflection hologram in a Fizeau geometry. To do this, we combined standard phase shifting with an iterative algorithm to solve for errors in the phase steps, obtained a phase surface, and ultimately fit it to a set of Zernike polynomials. Preliminary results show that we can characterize a surface via Zernike coefficients using in situ holographic exposures followed by a sequence of interferograms using small (<100μm) values of lateral shear.