title: Three-flat test with plates in horizontal posture.
abstract: Measuring flats in the horizontal posture with interferometers is analyzed in detail, taking into account the sag produced by gravity. A mathematical expression of the bending is provided for a plate supported at three unevenly spaced locations along the edge. It is shown that the azimuthal terms of the deformation can be recovered from a three-flat measuring procedure, while the pure radial terms can only be estimated. The effectiveness of the iterative algorithm for data processing is also demonstrated. Experimental comparison on a set of three flats in horizontal and upright posture is provided.
authors.affiliation: Consiglio Nazionale delle Ricerche, Istituto Nazionale di Ottica Applicata, Largo E. fermi 6, Firenze, Italy. maurizio.vannoni@inoa.it
authors.forename: Maurizio
authors.initials: M
authors.lastname: Vannoni
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Molesini