NIMO: a new tool for asphere and free-form optics measurement

Abstract

NIMO is a new measurement tool based on the Phase-Shifting Schlieren technique [1]. The technique combines the Schlieren principle with the phase-shifting technique generally used in interferometry. By an adequate Schlieren filter and an adapted set-up, some Schlieren Fringes coding light beam deviation angles are generated. After the application of the phase shift technique, the Schlieren phase is calculated and converted in beam deviation values. The technique has been validated on conventional optical element ranging from millimetre to decimetre scales. NIMO opens a new step in metrology in a wide industrial range in both reflection and transmission (e.g. optical manufacturing, glass industry, ophthalmic industry,…). In [2],we focused on fluid physics applications and the implementation of the technique in a microscope for MEMS measurements. In [3], we described an adapted setup in which all the phase shifted images are acquired simultaneously opening the possibility to measure dynamic phenomena with NIMO. This paper is focused on the instrument recently developed for ophthalmic industry. The performances of the instrument are given and industrial applications in free-form and aspherical surfaces metrology are demonstrated.