title: Optical metrology for two large highly aspheric telescope mirrors.
abstract: We describe a relatively simple, but highly effective, approach to the system design and alignment of an all-refractive Offner null corrector and phase-measuring Shack cube interferometer. In addition we outline procedures for fabricating and testing the optical components. Allowable errors for all parameters are determined by a tolerance analysis that separates axisymmetric and residual figure errors. An open construction optics frame provides a high degree of metering flexibility by incorporating simple kinematic mounts that provide adjustment of each lens while also allowing the lens to be removed and replaced with <2microm absolute repeatability. Nonaxisymmetric alignment errors are removed by rotating the optics on a high-precision bearing. Axial spacings are measured with contact transducers attached to both ends of an Invar metering rod. Two completed systems have guided the stressed-lap polishing of 1.8-m f/ 1.0 and 3.5-m f/ 1.5 aspheric mirrors.
authors.forename: S C
authors.initials: SC
authors.lastname: West
authors.forename: J H
authors.initials: JH
authors.lastname: Burge
authors.forename: R S
authors.initials: RS
authors.lastname: Young
authors.forename: D S
authors.initials: DS
authors.lastname: Anderson
authors.forename: C
authors.initials: C
authors.lastname: Murgiuc
authors.forename: D A
authors.initials: DA
authors.lastname: Ketelsen
authors.forename: H M
authors.initials: HM
authors.lastname: Martin