Isotropic image in structured illumination microscopy patterned with a spatial light modulator

We developed a structured illumination microscopy (SIM) system that uses a spatial light modulator (SLM) to generate interference illumination patterns at four orientations - 0°, 45° 90° and 135° to reconstruct a high-resolution image. The use of a SLM for pattern alterations is rapid and precise, without mechanical calibration; moreover, our design of SLM patterns allows generating the four illumination patterns of high contrast and nearly equivalent periods to achieve a near isotropic enhancement in lateral resolution. We compare the conventional image of 100-nm beads with those reconstructed from two (0° -90° or 45° -135° ) and four (0° -45° -90° -135° ) pattern orientations to show the differences in resolution and image, with the support of simulations. The reconstructed images of 200-nm beads at various depths and fine structures of actin filaments near the edge of a HeLa cell are presented to demonstrate the intensity distributions in the axial direction and the prospective application to biological systems.