Optical simulation of device efficiency and contrast ratio for a digital micromirror device

Abstract

We present an electromagnetic simulation of a digital micromirror device (DMD) that models optical performance from the visible spectrum to the mid-wave infrared regime. We calculate DMD efficiency, including the effects of optical scatter and interference, over a wide range of focal ratios (f/2.8 to f/8) and wavelengths (0.4 μm to 5 μm). Furthermore, we investigate how contrast ratio varies with respect to wavelength, provided a set of operating parameters. The micromirror array structure of a DMD induces strong wavelength-dependent optical effects that impact the stray light and throughput of a system. To quantify this, we perform a three-dimensional electromagnetic finite-difference time-domain simulation where we illuminate the DMD with a focused, diffraction-limited beam; calculate the near-field electric field; and transform the distribution of light to the far-field. We characterize the performance of a DLP7000 device in three key wavelength regimes: the specular regime (λ < 1 μm), the transition regime (1 μm < λ < 3 μm), and the diffraction regime (3 μm < λ < 5 μm). Our results inform optical performance parameters and provide design constraints for the implementation of DMDs in sensitive optical instruments.