Abstract
Digital micromirror devices (DMDs) are spatial light modulators that employ the electro-mechanical movement of miniaturized mirrors to steer and thus modulate the light reflected off a mirror array. Their wide availability, low cost and high speed make them a popular choice both in consumer electronics such as video projectors, and scientific applications such as microscopy. High-end fluorescence microscopy systems typically employ laser light sources, which by their nature provide coherent excitation light. In super-resolution microscopy applications that use light modulation, most notably structured illumination microscopy (SIM), the coherent nature of the excitation light becomes a requirement to achieve optimal interference pattern contrast. The universal combination of DMDs and coherent light sources, especially when working with multiple different wavelengths, is unfortunately not straight forward. The substructure of the tilted micromirror array gives rise to a blazed grating, which has to be understood and which must be taken into account when designing a DMD-based illumination system. Here, we present a set of simulation frameworks that explore the use of DMDs in conjunction with coherent light sources, motivated by their application in SIM, but which are generalizable to other light patterning applications. This framework provides all the tools to explore and compute DMD-based diffraction effects and to simulate possible system alignment configurations computationally, which simplifies the system design process and provides guidance for setting up DMD-based microscopes.This article is part of the Theo Murphy meeting ‘Super-resolution structured illumination microscopy (part 1)’.
Highlights
Spatial light modulators (SLMs) offer a robust and fast way to pattern the excitation light in a fluorescence microscope
All diffraction images shown in this article were simulated with m = 7.56 μm micromirror pitch and γ ± = ±12◦ as tilt angle, which corresponds to the dimensions of the DLP® LightCrafterTM 6500 (Texas Instruments) [26] and some other Digital micromirror devices (DMDs)
The use of FLCoS-SLMs requires the implementation of a much more complicated timing scheme because of the limited duration during which a specific pattern can be projected by these devices
Summary
Spatial light modulators (SLMs) offer a robust and fast way to pattern the excitation light in a fluorescence microscope. Digital micromirror devices (DMDs), on the other hand, work electro-mechanically, by individually flipping the orientation of each mirror between two pre-defined states Because of their widespread use in consumer devices such as video projectors, DMDs are available at relatively low cost and in a variety of sizes. They offer high switching speeds, they can handle high light intensities, and depending on coating, are not sensitive to light polarization. If DMDs are selected as active light modulation systems in a fluorescence microscope based on laser light sources, this effect must be well understood and needs to be taken into consideration
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