Micromirror arrays (MMA) are spatial light modulators (SLM) used in a wide variety of applications for structured light manipulation <i>i.e.</i> structured illumination microscopy.<p> </p> In our setup, we use a combination of two micromirror arrays, which allow not only to spatially structure the light in the field of view, but also to control the direction and angle of the incident light. In order to achieve this, a first MMA is imaged in the focal plane and used as a black and white (or even greyscale) mask. With a fully illuminated objective, this image would normally be formed from the complete light cone. By imaging the second MMA onto the backfocal plane of the objective only a portion of the light cone is used to form the image. This enables avoiding the unwanted illumination of out of focus objects. The MMAs in our setup consist of an array of 256x256 micromirrors, that can each be individually and continuously tilted up to 450nm, allowing the creation of greyscale images in real time in the illumination pattern. The mirrors themselves can be tilted for times as short as 10μs up to several seconds. This gives unprecedented control over the illumination times and intensities in the sample. Furthermore, our enhanced coating technology yields a high reflectivity over a broad optical spectrum (240- 1000nm). <p> </p>Overall, the setup allows targetted illumination of subcellular regions enabling the precise, localized activation of optogenetic probes or the activation and deactivation of signaling cascades using photo-activated ion-channels.
Diffractive micromirror arrays (MMA) are a special class of optical MEMS, serving as spatial light modulators (SLM)
that control the phase of reflected light. Since the surface profile is the determining factor for an accurate phase
modulation, high-precision topographic characterization techniques are essential to reach highest optical performance.
While optical profiling techniques such as white-light interferometry are still considered to be most suitable to this task,
the practical limits of interferometric techniques start to become apparent with the current state of optical MEMS
technology. Light scatter from structured surfaces carries information about their topography, making scatter techniques
a promising alternative. Therefore, a spatially resolved scatter measurement technique, which takes advantage of the
MMA’s diffractive principle, has been implemented experimentally. Spectral measurements show very high contrast
ratios (up to 10 000 in selected samples), which are consistent with calculations from micromirror roughness parameters
obtained by white-light interferometry, and demonstrate a high sensitivity to changes in the surface topography. The
technique thus seems promising for the fast and highly sensitive characterization of diffractive MMAs.
Photoactivation and “optogenetics” require the precise control of the illumination path in optical microscopes. It is equally important to shape the illumination spatially as well as to have control over the intensity and the duration of the illumination. In order to achieve these goals we use programmable, diffractive Micro Mirror Arrays (MMA) as fast spatial light modulators for beam steering. By combining two MMAs with 256×256 mirrors each, our illumination setup allows for fast angular and spatial control at a wide spectral range (260-1000 nm). Illumination pulses can be as short as 50 μs, or can also extend to several seconds. The specific illumination modes of the individual areas results in a precise control over the light dose to the sample, giving significant advantage when investigating dosage dependent activation inasmuch as both the duration and the intensity can be controlled distinctly. The setup is integrated to a microscope and allows selective illumination of regions in the sample, enabling the precise, localized activation of fluorescent probes and the activation and deactivation of cellular and subcellular signaling cascades using photo activated ion channels. The high reflectivity in the UV range (up to 260nm) further allows gene silencing using UV activated constructs (e.g. caged morpholinos).
The ability to control the illumination and imaging paths of optical microscopes is an essential part of advanced
fluorescence microscopy, and a powerful tool for optogenetics. In order to maximize the visualization and the image
quality of the objects under observation we use programmable, fast Micro Mirror Arrays (MMAs) as high-resolution
Spatial Light Modulators (SLMs). Using two 256x256 MMAs in a mirror-based illumination setup allows for fast
angular-spatial control at a wide range of wavelengths (300-1000nm). Additionally, the illumination intensity can be
controlled at 10-bit resolution. The setup allows selective illumination of subcellular regions of interest enabling the
precise, localized activation of fluorescent probes and the activation and deactivation of subcellular and cellular
signaling cascades using photo-activated ion-channels. Furthermore, inasmuch as phototoxicity is dependent on the rate
of photo illumination  we show that our system, which provides fast, compartmentalized illumination is minimally