Laser-modulated Lissajous scanner for structured illumination microscopy

Abstract

High resolution microscopic imaging technique has been steadily demanded to observe detailed structures or dynamic mechanisms of biological samples. Structured illumination microscopy (SIM) has grabbed much attention due to its simplicity, compatibility with common fluorescent molecules, and fast image acquisition. Here we report Lissajous scanning SIM (LS-SIM) by using Lissajous scanning micromirror and laser intensity modulation. Biaxial scanning frequencies of Lissajous micromirror are substantially separated to avoid mechanical coupling and the fast axis inner mirror has a relatively low Q-factor to obtain a broad selection range of scanning frequency. A Lissajous trajectory of high fill-factor is achieved with a selected set of scanning frequencies at pseudo-resonance, where Lissajous scanned structured illumination (SI) is realized by modulating a laser beam at least common multiple (LCM) of bi-axial scanning frequencies. A compact Lissajous scanned SI module, containing fiber-optic collimator and Lissajous micromirror is fully packaged, coupled with fiber-based DPSS laser with acousto-optic-modulator (AOM) and mounted with a conventional fluorescent microscope. The LS-SIM clearly demonstrates high-resolution microscopic imaging after the image reconstruction of various imaging targets. This method will provide many potentials for diverse fluorescence microscopic applications.