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Phase measurement of optical wavefront by using an SLM knife-edge filter

Author(s): Hideo Furuhashi, Javier Valle Mayorga, Yoshiyuki Uchida, *Akihiro Kono
Affiliation(s): Aichi Institute of Technology, *Nagoya University

Topic: 1. Interferometry & Optical Testing Techniques
Presentation: Poster

Phase measurements of optical wavefronts are of considerable interest for many applications in optical testing, material diagnostics and microscopic analysis of living cells. There are many techniques based on the phase contrast method. Of one these techniques is the Schlieren method that employs a knife-edge. It enables qualitative visualization of the phase derivative. It is necessary to scan the filter in order to obtain quantitative measurements over a wide range of the phase derivative. Some studies have reported mechanical scanning of the knife-edge. In this paper, a spatial light modulator (SLM) is used as a knife-edge filter that can be varied electrically to qualitatively measure wavefronts. Using an SLM enables not only the filter position to be changed, but also the filter direction. Knife-edge filters can visualize the phase derivative only in the direction perpendicular to the edge. Therefore, the knife-edge filter needs to be rotated in order to obtain the phase derivative in another direction. The orientation of the SLM filter can be controlled electrically. The phase derivative of a wavefront passing through a transparent phase object has been measured. The 3D shape of the object was calculated by integrating the phase derivative.