Measurement of the scale distortion of a digital micro-mirror device in a 4f-imaging system

Abstract

A digital micro-mirror device (DMD) consists of numerous micro-mirrors that can be electronically controlled to modulate incident light through reflection. However, DMD models with diagonal mirrors use an unusual indexing scheme that causes a stretch-distortion to uploaded patterns. Patterns must first be rescaled with the proper scale factor before uploading to the DMD to remove the distortion. We present a systematic method to measure the scale factor of a DMD when it is used in a 4f-imaging system. We place a circular aperture at the input plane of the 4f to project an Airy pattern onto the DMD. Elliptical slits with varying eccentricities were uploaded to the DMD that selectively isolates a bright ring in the Airy pattern. Intensities detected at the output plane of the 4f resemble a caustics pattern, which collapses to a point when the proper scale factor was used to generate the slit.