Freeform optical surface shapes have evolved from an intriguing optical design concept to a practical necessity for applications ranging from space and defense to consumer electronics. The demand for freeform solutions is no more strongly felt than in the development of digital immersive displays for augmented and mixed reality, where the combination of exceptionally high performance combines with ergonomic constraints of wearable interactive technologies. Some of these advanced designs call for diffraction-limited performance at large fields of view in off-axis orientations, often through conformal surfaces. Freeform optics are often the only way to correct the resultant aberrations, but their manufacture demands high-precision, high resolution surface figure metrology data such as can be obtained using coherence scanning interferometric microstitching (CSIM).