Abstract
A novel 3D patterned illumination system using an incoherent light source has potential benefits for structured illumination microscopy (SIM) such as lowered intensity requirements and tunable modulating frequency. The illumination system, based on a coherent source, a set of parallel slits and a beam- splitting Fresnel biprism, generates localized interference fringes with a continuously- tunable range of lateral and axial spatial frequency combinations that are not easily accessible using other existing methods of generating structured illumination. Here we present adaptation of this system to a wide- field fluorescence microscope that tests its suitability for SIM imaging. Numerical simulations and experimental data are used to compare theoretical and practical system properties. Results demonstrate that theoretically predicted illumination properties can be used to select system design parameters and accurately produce specific illumination properties at the microscope sample plane. As part of an imaging system, this illumination approach may improve the applicability of super- resolution SIM to a greater variety of samples.