Structured illumination microscopy using digital micro-mirror device and coherent light source

Structured illumination microscopy (SIM) achieves doubled spatial resolution through exciting the specimen with high-contrast, high-frequency sinusoidal patterns. Such an illumination pattern can be generated by laser interference or incoherent structured patterns. Opto-electronic devices, such as a Spatial Light Modulator (SLM) or a Digital Micro-mirror Device (DMD), can provide rapid switch of illumination patterns for SIM. Although the DMD is much more cost-effective than the SLM, it was previously restricted in association with incoherent light sources, as its diffractive orders are related to the incident angle and the wavelength of coherent incidence. To extend its application with coherent illumination, here, we model the DMD as a blazed grating and simulate the effect with DMD pattern changes in the SIM. With careful analysis of the illumination contrast along different angles and phases, we report a fast, high-resolution, and cost-efficient SIM with DMD modulation. Our home-built laser interference-based DMD-SIM (LiDMD-SIM) reveals the nuclear pore complex and microtubule in mammalian cells with doubled spatial resolution. We further proposed the multi-color LiDMD-SIM concept by jointly employing the DMD ON/OFF states with different incident angles for different wavelengths, with high contrast and maximum resolution enhancement.