What types of things can be measured using a CGH?
CGHs are used as an accessory to an interferometer, which nominally measures flat or spherical test optics.
CGHs are used to measure Surface Figure Error of aspheric or freeform optics.
CGHs can also be used with an interferometer to measure Transmitted Wavefront Error of a Subassembly.
CGHs can also be used to Align and Assemble Multi-Element Assemblies.