Interferometric measurement of geometry and image quality of non-spherical surfaces - using two-beam interferometer with adjustable phase between measurement and reference paths

摘要

Interferometric measurement of the geometry and imaging quality of a non-spherical optical element or system (8) involves placing it in the aperture matched test beam path of a two-beam interferometer in which the phase between the reference and test paths is adjustable. Interferences are detected photoelectrically and evaluated by a computer. A spherical wavefront optimally matched to the measurement element, and with an aperture at least as large as the element's aperture, is produced by a further element or system (7) in the other path. The focal point of the further element is moved stepwise into the focal range (AB) of the measurement element by a positioning system (11). Resulting zone interferences are detected and used to determine the total aperture range of the measurement element or system.