Geometrical characterization of micro-optical cylindrical lens arrays using angular resolved diffraction

Abstract

The versatility of micro-optical lens arrays (MLA) is giving rise to many new applications often to be included in mass-produced parts and systems. The need for fast and robust methods of characterization and quality control, addressing an industrial manufacturing environment, is evident. It has been shown (Iversen et al 2009 J. Opt. A: Pure Appl. Opt. 11 054014 (6pp), Büttner and Zeitner 2002 Appl. Opt. 41 6841–8) that the average radius of curvature of an MLA structure can be extracted by observing the far-field diffraction pattern intensity distribution obtained from illumination of the MLA structure with a coherent light source. This method is based on a priori knowledge of the grating period. We here present a method that fully characterizes the geometrical properties, i.e. the grating period and the average radius of curvature of an MLA structure in a single measurement cycle. By scanning the angle of incidence of the coherent illumination and simultaneously observing the diffracted intensity, information about the grating period and the radius of curvature can be extracted. The method is implemented with emphasis on further development for compact, high-speed dedicated systems. We present experimental data extracted from two different MLA structures using the proposed method. The results are compared with atomic force microscopy measurements of the MLA geometry.