New technique for flexible and rapid measurement of precision aspheres - art. no. 661629

A new interferometric technique for the measurement of aspheric elements based on multiple test beams is presented. By means of an array of sources (Point Source Array) an aspheric surface is illuminated under different angles-which allow the measurement of the zones where the local gradient of the test piece is compensated. One of the main advantages of the system is that the measurement process is performed in parallel (many sources are used at the same time) thus requiring extremely short measurement time in comparison with other available subaperture testing techniques. Another important aspect is that the asphere stays in the same position during the whole process; there are no mechanical movements of the test part involved. The technique allows the measurement of strong aspheric elements with departures from the best fit sphere up to +/- 10 degrees. The method was developed to obtain accuracies of up to lambda/30 and better. Simulations and first experimental results are presented.