Synthesis of Arbitrary Interference Patterns Using a Single Galvanometric Mirror and Its Application to Structured Illumination Microscopy

Structured illumination microscopy (SIM) overcomes the diffraction limit of optical microscopy by projecting finely spaced interference fringes with different orientations and phases onto the sample and imaging the result. A major challenge of SIM is to generate the different illumination patterns with a high contrast and switching speed, which commonly requires expensive devices and the sacrifice of illumination power efficiency. We present a new way of generating interference patterns for 2D and 3D SIM achromatically, with high speed and high power efficiency, using only one moving part. The interference patterns are created by a common-path interferometer, with the orientation, polarization, and phase of interference patterns controlled by a single galvanometric mirror. We characterize the contrast and switching speed of the interference patterns and demonstrate their utility by performing high-speed (980 raw frames per second) 2D SIM imaging on fluorescent nanoparticles and 3D SIM on fixed iFluor 488 phalloidin-stained U-2 OS cells.