Mach-Zehnder / Twyman-Green hybride interferometer for micro-lens testing

An alternative interferometer design for micro-lens testing is presented. The phase shifting system combines the advantages of a Twyman-Green and a Mach-Zehnder interferometer and allows full characterization of the aberrations of micro-lenses as well as radius of curvature and focal length measurements. The Twyman-Green system is applied to surface testing in reflection whereas the Mach-Zehnder system is used for lens testing in single pass. Both measurements are performed without removing the test part, allowing a combination of the results without confusion of the actual lens and without an azimuthal orientation error. The interferometer setup is explained, the test procedure is described and experimental results are given.